Via Thunder Rumblings:
Well, at least it wasn't the teams fault this time.
Presumably, someone on the development team for NBA2K9 decided to post a video with the Thunder jerseys in it. The NBA probably required the Thunder to give it to 2K Sports early, so it could be in the video game.
This image, from NBA Live 09, shows another variation on the uniforms. This one looks like it was from an Alpha though, as the scoreline is formatted poorly and the graphics look like they're from NBA Live '99.
Only time will tell, but if I had to guess, I'd lean towards the video being a more realistic representation of the uniforms. We'll all see on Monday's Media day.
Side Note: Did anyone see the super slick presentation in NBA 2K9? Damn! The first game to include actual video since NBA 2K6, and the way everything is done makes me feel like I'm actually watching TV. The line between TV and Video games continues to become more and more blurred....
EDIT: New Photos, Via Thunderworld. Looks like the uniforms are pretty much confirmed. These unis are the same as the 2K version, except from NBA Live 09.