Remember, we need to take into consideration that he's going to play 81 games at Wrigley Field. It doesn't take a genius to know that when the wind blows, balls fly outta that park.
If Peña could hit 47 at Tampa, he can easily hit 40 in Chicago -- even if he hits .250.
Edit: @GIANTS=CHAMPIONS, dude, you're right. The NL Central has Yovani Gallardo, Zack Greinke, Shaun Marcum, Chris Carpenter, Adam Wainwright, Jaime Garcia, Johnny Cueto, and Bronson Arroyo, but something that hasn't been addressed is that they can allow homeruns.
These are the homeruns allowed by these 8 pitchers last season:
These guys are good, but not untouchable. Peña can catch up to the best heater they can throw him. People don't give the guy enough credit, but I can't blame you.