He said this in a chat at EXPN.com. Website PlanetGameCube contacted publisher Acclaim about this, and they confirmed the story. Not only will his name be removed from the title, his whole character has been taken out of the game.

Dave Mirra said in the chat that the reason for this move was because the game has been M-rated. You can read the chatscript here.

Acclaim and Dave Mirra won't split up though. He has just renewed his contract for another five years, so he will star again in future titles.

Source: EXPN.com, PlanetGameCube