They would have said the same about flights to South America from Dallas and Atlanta had American and Delta not dumped 500+ flights a day into each airport.
It would be insanely stupid if UA dumped the US hub and route structure on the east coast. Why spend the money the acquire an airline to then completely dismantle the route system. Look at the AirCal and PSA mergers with AA and US, what of those airlines route structures are left in the current route maps for American and USAir? The more I think about it Pittsburgh is a something that I think United would want to keep. The airport can expand fairly readily, I think it can support double or triple independant IFR arrivals, it has a big terminal with tons of space. United is boosting Charlotte as a competitor to Atlanta. It is a rapidly growing city with a variety of industry in the region. It is a good n/s connector, and some flights to Latin America would not be out of the question (see above). Baltimore is not much of US hub anymore, most ops are either express or MetroJet. Philly is at some risk because I don't really see how it fits in. Connections in the northeast could just as well be made at Pittsburgh or Dulles. And the European flights would likely be transfered to ORD, CLT, or IAD.
However any of this is in the long-term... 5 years before major changes would be noticable, with the exception of a Charlotte build-up. It is fun to speculate about this, but I still doubt more and more that this will go through.
Stop drop and roll will not save you in hell. --- seen on a church marque in rural Virginia