UFC president Dana White has confirmed that Lesnar is legally able to appear, as he is no longer under UFC contract. White said he didn't know if Lesnar would appear, though. Lesnar left WWE in March 2004 after WrestleMania XX for an NFL career before a stint with New Japan. He signed with the UFC after.
An AP writer noted in an article on the Rock that if WWE wanted another potential blockbuster match for the Rock, the best man would be Lesnar. When asked for comment, a grinning Rock said, "I'm not saying a thing. I didn't say anything."
Dave Batista is in Miami, FL as well. He's been in talks with WWE but it's not confirmed that he'll appear at the big event.
Despite Batista and Brock Lesnar being in Miami, FL right now, they are NOT confirmed for WrestleMania as of this writing. They are both in negotiations with WWE though.
-- WWE will have a SmackDown-brand house show on June 23 at at the Prairie Capital Convention Center in Springfield, Illinois. Tickets go on sale on April 28th.
-- The WWE Vintage Collection from March 30th, 2012 had the following matches:
The Shockmaster vs. The Equalizer
WCW Clash Of The Champions - November 10th, 1993
The Legion Of Doom vs. Demolition
WWF TV Taping - November 20th, 1990 - Syracuse, New York
Rey Mysterio, Super Calo & Hector Garza vs. Psychosis, La Parka & Silver King
WCW Saturday Night - January 17th, 1998
Hardcore Battle Royal
WWE Raw - August 19th, 2002
Steve Austin vs. Yokozuna
WWF Summerslam 1996 Pre-Show
Bret Hart vs. Shawn Michaels
WWF Wrestling Challenge - February 10th, 1990