MMA Weekly brought up the rumor in a recent Q&A:

MMAWeekly: EA took notice and shortly after the release of THQ's game, announced its own MMA game. Reportedly they are so intent on making their MMA game a success that they took teams off their NASCAR series to work on it before ultimately cancelling this year's NASCAR game all together. What do you think about that?

Blair Herter: Every time we speak, the one thing that everyone talks about that's been covering MMA is how much the sport has exploded and is exploding and how big it's getting. I think that just says it right there. That they're willing to pull teams from what is a big franchise for them and jump into (the MMA) market while not having the UFC on board, I think says a lot about how much of a market EA thinks there is for another MMA game.

You may remember Blair Herter as a participant of Road Rules season 6.17999 repeating. Herter now works for G4, which makes him a videogame expert though the only bit of information that is remotely interesting is the point about Electronic Arts removing teams from their NASCAR game to work on the MMA game though all Blair can say is "explode" or "explosion" over and over again (he's sooo extreme!).

WKR isn't positive that the assertion that EA took teams off of NASCAR '10 is accurate. Electronic Arts exclusive deal with NASCAR expired in 2009 (the year '10 would've come out) and we can't find an actual product listing for NASCAR '10 at IGN.com. Also, EA made bad NASCAR games --the '08 and '09 versions scored a 5.0 and 5.9 out of 10 at IGN.com-- so there is no reason for NASCAR to re-up with EA. From what we've read it appears that EA ported the '09 version to the Wii and called it a series for economic reasons.

EA Sports MMA is expected to be released in the fourth quarter of 2010. Fighting Spirit Magazine reported that the game is set for a September release.

Update: WKR is not trying to say that EA didn't divert teams. Rather, that there were other factors that contributed to the purported movement of development teams.

Update #2: Good video of fighters discussing EA Sports MMA