Here's a great analysis from Baseball Prospectus of Teahen's breakout season and what it means for his future.

http://www.baseballprospectus.com/article.php?articleid=5476

The conclusion is a happy one.  Historically, guys like MT have held on to power gains similar to the gains he's made this year.  That is, even though it's a relatively small sample size (300+ ABs and counting...) it looks as if his power spike is no fluke.