WTF, east of the Mississippi is where the majority of domestic travel profits are. So many senior folk between the the two airlines, don't think the SLI issues will be as bad as you think.
True, I just wonder about hubs in PHL, CLT and MIA. Remember that USAirways route system was concentrated doing East coast N-S flying for many years and they didn't do well for much of that time. It's so saturated that if these carriers combine they will probably cut capacity back to reduce overlap and increase profit margin. We will see about the SLI issues, maybe I'm wrong but I think it will be very difficult, the list at LCC hasn't been resolved yet. USA East and American are two of the most militant pilot groups on the planet and they have two different unions.