I think he retired, but appears to be filled with torment about a possible return, as is Erik Morales. They should both let it go IMO - no point carrying on once shot, and these two clearly are.
http://news.bbc.co.uk/sport2/hi/boxing/7029046.stm Barrera retired. While we all know how lasting boxing retirements usually are, Barrera may be the exception. He's a sharp, educated guy who made a ton of money in the sport. I believe he has or was working towards a law degree, so there's life after boxing for him.
Barrera, along with Morales, announced retirement after the Pac and Diaz fights, repectively. But yeah, I heard the two are talkin' about comin' back. They both have gas left in 'em. Marco didn't do bad against Pac and Erik lost a controversial dicision against David Diaz. I'm torn on El Terribles retirement and had very much welcomed Marco's. But again, I think the two of them have a few good fights left between the two of them.