Well the tanks and hummers (military ones at least) run on diesel which should have been fine for the generators if not their own vehicles but there is the chance that the scientist did drain them to prolong his research but the director didn't feel like wasting the 10 seconds it would have taken to explain it

On the other hand, they didn't really have enough time to siphon and feed the generators since they all waited until the clock was down to 1 hour before asking what it was for... Not asking what a timer is for (to me at least) is like not asking what the shiny red button does before leaning right next to it. A very Darwin Award worthy mistake to say the least.
Yeah, Merle's character (handcuffed racist) and his brother are bound to play a larger role somewhere down the story line, I can just feel that. Hell, I think everyone that gets more than a line or two is going to die a horrible agonizing death sooner or later but I'll keep watching just to see how the interplay works out before they bite it!
If they decide to stay close to the original storyline (which I got a brief synopsis of from my friend who read it), they'll be going to a prison next where they'll set up a more permanent 'camp'. I have a feeling that is what the scientist whispered into his ear there at the end, the location. I could be wrong as I don't don't know exactly how they decided to go to the prison in the first place, but that is where the bulk of the story took place.