Thanks Grizzly, this article says they still don't have the date, but will be out by Apr. 25th (a month before the game) and that you can play exhibition or tournament mode with those four fighters you mentioned.
UFC Undisputed 2010, the second iteration of the THQ produced UFC video game, hits store shelves on May 25, 2010. However, gamers will get a chance to check out the new and improved gameplay of the 2010 version with a demo coming to the PlayStation Network and Xbox Live.
According to the production blog at UFCUndisputed.com, while no release date is set for the demo, they are hoping to release it at least a month before the game is released, which would bring it to both platforms sometime before the end of the month.
The demo will feature four light heavyweight fighters in division Champion Lyoto Machida, his next challenger Mauricio "Shogun" Rua and TUF 10 coaches and UFC 114 headliners Quinton "Rampage" Jackson and Rashad Evans. Players will be able to play the Exhibition mode, as well as an offline multiplayer Tournament mode.