Danders is right, Cargoflyr69, Shuttle America has more departures than any other express carrier in PIT, and possibly more than mainline if I remember correctly (though I may not, so no quoting please).
Yes, PIT is our primary hub, with every scheduled flight in our system going to or from there with the exception of BED-TTN and TTN-BED... And even THAT was supposed to go away but due to customer demand we are staying there for the time being. The fact that Boston-Maine announced that THEY were going to do that run after we announced we were leaving means there's actually COMPETITION on that route, but the level of that competition remains to be seen.
The new deal with UA means that our new hub will be Dulles, but it doesn't necessarily mean that there'll be a crew base there. I've heard "yes, there will be, but a small base" and "no, there won't be", and I don't know which to believe. Guess we'll find out once the planners figure out what we're going to do. Weasel Keeper answered the other question, FWA remains the MX base and will remain a crew base, though a relatively small one (1/3 current size), and aircraft will be repo'd back and forth to and from maintenance at scheduled intervals. This will also allow people to get to and from FWA for training and for those who are based in FWA.
Anything else beyond this, I think, is purest speculation.