Winning a bunch of gold medals? Yeah, I guess that's pretty rad. But if he can somehow be a part of an Olympic-style swimming game that isn't complete garbage, I'll be totally blown away. I'm pretty sure there hasn't been a serious Olympic track and field sports game that's been any good since, like, Track & Field.
No real details on the game or who's producing it turned up in the original article, but if he's got an agent that's rejecting a bunch of lesser endorsement deals, hopefully they know better than to pair up with anyone responsible for... well... any of the Olympic video games that have been released in the last decade. Considering Phelps is already doing business with Activision (and is, as you've probably heard, a big Call of Duty 4 fan), the speculation points in that direction.
Maybe instead of going down the dreary sports path, they'll just cast him as the lead in a first-person shooter and make a modern-day Shaq-Fu or Michael Jordan: Chaos in the Windy City. But with swimming or something. Call it Michael Phelps Saves the Orphanage By Swimming and Shooting A P90 and I'm so in.