I think he will come back down to earth. There's a reason why Pena has played for five teams (six if you count the Yankees, he played for Columbus most of '06, before he was released and signed with the Red Sox for a few games).
Carlos Pena has some serious power, but I don't see him hitting 46 home runs again. Maybe 25-30 if he's lucky, but like a lot of guys, he had one dream season. I'm not knocking Pena, he is a really nice guy, and he's interesting when you hear him talk. He's also a Gold Glove-caliber guy. It's just hard to see a journeyman like him having another like he did last year, or anything close to that.