Yes I think there is a possibility that liberals will rally against Obama's drone program because of what it entails. I think that since it was a secretive program and most people knew very few, if any, details, people are going to be reacting against it. It is a bad program.
There are already many liberal organizations and activists who have stood up against the drone program and the use of drone strikes. Well-known media figures, like Bill O'Reilly and Jon Stewart, have also said publicly how the drones are a horrible idea and infringe on people's rights. So I do think this will happen.
It really isn't a liberal or conservative thing. While all conservatives will rage about it because they do so blindly about anything Obama does, there are people on both sides that aren't really on board with his "kill list" and how it's being utilized. He hasn't done anything unforgivable yet but the checklist for things needed to whack somebody with a drone strike is little more than "I feel like it" and that's worrisome.
The drone program isn't the main issue here, and rallying against one small symptom of a larger problem isn't going to produce change in the larger scope of the war(s) that liberals are staunchly against. I say won't because I believe liberals will see the larger scope and spend energy rallying against the root cause.