After thinking about this a little more, the new US Airways will probably focus on PHX, PHL, and CLT. I see PIT disappearing sooner rather than later. The continued usage of LAS most likely depends on the availability of aircraft at night for increased utilization.
Convention wisdom says that you need a hub in the middle of the country. However, we now have RJ's that can fly 3+ hours. Perhaps that middle hub is no longer needed. On the other hand, there's a whole terminal available at DFW...