According to the WSJ, Obama called Scottie Brown to let him know immigration reform was coming down the pike in about a month, presumably on the theory that Brown is the Senate's Gossip Girl.
Getting the process started by the end of May seems more like a genuine effort to get legislation passed, rather than a purely political move to put the issue on the table (without any actual action on it) prior to November. Either way though, I think getting immigration reform out there is the right move. It'll galvanize the base, give Republicans big opportunities to alienate the center, and it won't cost Democrats votes that they hadn't already lost. Win-win-win.