Buster Olney just tweeted that the Race For Carlos Beltran is down to the following teams:
Boston, San Francisco, Philadelphia, Atlanta, Texas, and Cleveland.
Jon Heyman says that the Giants, Phillies, and Braves are the leaders for Beltran.
Now, the good thing - if you think trading Pence is a good and necessary move - is obviously that there is more demand for elite Right Fielders than there are elite Right Fielders, and yeah, I consider Pence an elite Right Fielder. If Philly or Atlanta end up with Beltran, you can reasonably expect that the other is going to try to counter with Pence. The AL Central is a crap-shoot, as is the AL West, so a player like Pence can change the outcome of those races. Boston's going to make the playoffs regardless (likely, anyway).
But aside from the Giants (whom I know very little about, except that they have Jack Keplinger), the other teams have prospects that could impact the Astros for years to come.