Gerlach has an incentive to do something, since his seat is so marginal, and he could lose it at any time, and has to work his butt off to hold it. But I can't imagine how Gerlach could be electable in the General if he took out Specter in a primary.
How he'd be electable? Gerlach appeals to the types of Republicans that might have been pissed at someone like Toomey knocking off Specter. Gerlach isn't polarizing (contrary to PA 6 results and especially not among Republicans). He wouldn't get destroyed in the SE and he's conservative enough to kick ass in the areas that he would need to win huge.