What's the future of the NBA in Seattle?

Kevin Durant played in the last Seattle SuperSonics game, a bittersweet moment when he had the finest game of his rookie season with 42 points, 13 rebounds and six assists but called the night "sad."

It's been 10 years now since the Sonics left Seattle and took the supernova that Durant was to become and the lottery pick that turned into Russell Westbrook with them. It's been a decade of empty promises, near misses and political infighting both in Seattle and the NBA itself that have kept a team away.

"It was very devastating how we up and left in the middle of the night," Durant said. "I know those fans have been yearning for basketball for a long, long time."

This week Durant returns symbolically for a preseason game with the Golden State Warriors, the first time there's been any NBA presence in the city since June 2008 when the move to Oklahoma City became official (Kings vs. Warriors, Friday, ESPN, 10:30 ET). The game coming to fruition was a passion project for Seattle native and Warriors' president Rick Welts, and it's raised the hopes of the throngs of Sonics fans who want the NBA back.

Seattle and the NBA have become an enigma. The city has the money; it's never been richer. There have been two competing groups willing to finance arenas with no public money. The city has the fan support: It's one of the most vibrant sports markets in the country. Hockey fans put down 32,000 season ticket deposits as the NHL recommended moving forward with plans to add a 32nd team in Seattle.

What it didn't have was an acceptable arena, the genesis of the reason the Sonics left. After numerous previous proposals failed, last week the Seattle City Council passed a measure to clear the way for a privately-funded rebuild of antiquated KeyArena, ensuring the city will have a world-class venue by late 2020 or early 2021. The end of the long journey triggered a wave of momentum not only that the NHL would come, but that the NBA would soon follow.

So that is the question: When will Seattle get the Sonics back?

The likely answer isn't what Seattle basketball fans want to hear: Not anytime soon.

The NBA doesn't have expansion anywhere on its timeline, and Seattle's arena developments weren't discussed for a moment at the fall board of governors meeting two weeks ago, league sources said. Some prospective ownership groups that have met with NBA officials have been told expansion may not happen until 2025 at the earliest, when a new TV deal can be negotiated, sources said.

Beyond that, the complexities of the so-called New Arena at Seattle Center, the building's working title, may make it challenging for Seattle to compete for a team if and when the time comes. The situation could even require Seattle to have a second new arena with the NBA team as the main tenant if the city wants to outbid other markets to attract a team, multiple ownership sources told ESPN.

NBA commissioner Adam Silver hasn't ruled out expansion in the long term but is also focused on markets outside the U.S. The NBA has been playing regular season games in Mexico City for the past few years and is soon to announce the launching of a G League team there for the 2019-20 season, a trial balloon of how an NBA team might function there.

"There are lots of terrific markets out there in the United States and some in countries attached to the United States who also have wonderful cities that could potentially house NBA teams," Silver said in June, a reference to the league's interest in Mexico City.

Other than expansion, the wild card for Seattle would be for a current NBA team to relocate. Several prospective ownership groups are watching the Memphis Grizzlies. The city of Memphis has some protections built into the Grizzlies' long-term lease with FedEx Forum, however lawyers who have reviewed the lease believe there is a possible window for the team to leave in 2021, multiple league sources said.

However, Grizzlies owner Robert Pera would have to sell the team in order to move it under the terms of the lease, and Pera has given no indication he plans to do so. Quite the opposite, actually. Earlier this year, Pera agreed to buy out some of his minority owners at a price that valued the team at nearly $1.3 billion, league sources said. At the time, Pera told season-ticket holders in a statement that "I am committed to Memphis as an NBA market and as the home of the Grizzlies."

Naturally, this issue is complex and fast-changing. It's hard to predict where the NBA will be on its 30 current markets when the KeyArena replacement is expected to be finished. But multiple NBA owners and league sources told ESPN that while the Seattle arena development is positive, it doesn't materially change their viewpoint on replacing the Sonics at this time.

Seattle is undaunted. As soon as the Warriors and Sacramento Kings finish playing Friday night, KeyArena will close for renovation. When it reopens, city officials believe they have a real chance at having an NHL and NBA team.

"We've got all the components of where the NBA wants to be," said Seattle Mayor Jenny Durkan, a longtime Sonics fan who counts watching Slick Watts get three steals and score eight points in the last 34 seconds of a miracle win in 1976 as one of her fondest memories.

"This arena is being constructed purposely to accommodate hockey, basketball and concerts. I've spoken to Adam [Silver] and communicated to him that we're interested."

The company that is redoing KeyArena, the Los Angeles-based Oak View Group, has plans for the NBA. The company is a powerhouse run by Tim Leiweke, who is one of the most experienced arena developers in the world, and Irving Azoff, the famed music manager. It's backed by Jim Dolan, owner of the New York Knicks and the Madison Square Garden Company.

Oak View is planning an ambitious engineering feat, which Leiweke is quick to point out is not a renovation but a new structure. The issue is that the arena's iconic roof has been designated a national historic landmark and can't be altered. The arena is also built into the side of a hill in a neighborhood that has turned more residential in the past decade with more than 40 former parking and vacant lots turned into housing as it sits near Amazon's world headquarters.

So to expand the outdated arena, Oak View is planning to dig down and around the roof and several exterior glass walls to gut and expand the building's footprint. First pegged as a $600 million project, Leiweke told ESPN the price tag is now projected at $750 million.

Leiweke, a former longtime top executive at AEG, has been a part of 18 arena construction projects in his career from Berlin to Shanghai to Staples Center in Los Angeles. He said this is perhaps the most complex project he's been a part of, putting it next to AEG's renovation of the Millennium Dome in London, another project where the roof had to stay intact as it became the O2 Arena.

When it's done, though, Leiweke said it will be ready to house an NBA team despite the challenges and the demands of a hockey team and perhaps more than 100 concerts dates per year.

"I've been a member of the NBA and NHL family for more than 40 years. I clearly understand the expectations and minimum standards that getting an NBA team to Seattle is going to demand," said Leiweke, who is also is the former CEO of Maple Leaf Sports and Entertainment, which owns the Toronto Raptors and Maple Leafs.

"From revenue to premium seat options and all of the other critical aspects. I understand what they want from a fan experience and game production standpoint. All of that knowledge and experience has been baked into what we're doing. We know what we have to do."

The New Arena at Seattle Center indeed promises to be a huge success. Oak View has partnered with billionaire investor David Bonderman and Hollywood producer Jerry Bruckheimer to pledge $650 million to get an NHL expansion team, which should be finalized by the end of the year. Live Nation is also a partner and will ensure a premium slate of concerts.

But that is also potentially the issue. With others in line to get lion's share of profits, an NBA team would be arriving last to the party. That could dim the NBA's desire to move into the market when more lucrative options may be available elsewhere, league sources said. In essence, it's possible Seattle might finally have an arena -- but the wrong arena for the NBA.

Leiweke insists this isn't an issue and refers to the numerous markets were NBA and NHL teams share an arena effectively. Times, though, are starting to change.

NBA teams in deep-pocket markets are looking to control their own buildings to capture new revenue. The Warriors' privately-financed new arena set to open next year in San Francisco is a game-changer: It will open a fountain of new revenue that will make other big markets jealous. Clippers owner Steve Ballmer is in the process of trying to build his own arena in large part because he earns tens of millions less per season than the Lakers in the same building.

This changing landscape is why investor Chris Hansen, who tried to buy and relocate the Kings to Seattle in 2013, is still planning to construct his own privately-financed arena in the SoDo district of Seattle near the baseball and football stadiums.

Hansen has run into road blocks getting the support of the city and neighboring dock workers. But he's still buying property and now has 13 acres. His arena wouldn't have the space and traffic limitations at KeyArena and could make an NBA team the primary tenant and therefore be more attractive.

But while this would be a strong alternate option, it literally isn't off the ground and would take longer. Possibly delaying Sonics fans' dreams of their team returning.

Ultimately, Seattle is going to have one and perhaps two new top-shelf venues to use and a new NHL team, possibly for the 2020-21 season, to cheer for. They will become an even more compelling market for an NBA team. But the aging green-and-gold merchandise is probably going to have to stay in the closet while the billionaires, politicians and executives scrap over the money and details.

"I have little doubt that this road ends with us having a competitive chance to have an NBA team," Mayor Durkan said. "We're being cautious, but we're watching very closely."

ESPN.com Insider Kevin Pelton and NHL reporter Emily Kaplan contributed to this story.