DJ Tiesto has issued a statement via his official newsletter claiming that a previous statement attributed to this official newsletter, which said that the DJ would be a part of an upcoming Activision music game called DJ Hero, was completely false and didn't come from him (or his newsletter) in the first place.
Here's the quote that CVG dug out of said newsletter:
"There has been a lot of talk concerning an alleged quote from Tiesto about being involved in Activision's possible DJ Hero video game. This information was based on a fictitious news items, posted on a third party online forum."
There's no actual denial in the statement, so it certainly seems possible that, if such a game does exist, that this guy could still be a part of it.
Just to further confuse things, don't forget that Activision also recently gave out details and screens for a supposedly separate turntable-based DJ game with a hip-hop theme, Scratch: The Ultimate DJ.