Competition always makes the market stronger. PIT has been a non-hub for sometime now, dontcha think somebody would've made a move there if the O&D was good?
Instead, WN goes to PHL. And PIT has CAK on its' flank.
PIT's unresolved & expensive airport bond situation must be resolved.
Unless/Until US pulls the hub, nobody else wants to come into PIT because they are fighting a losing proposition from a frequency/flyer loyalty standpoint. Airtran and America West both felt this.
When/if US pulls PIT down to a focus city and everyone has to connect anyway, the floodgates are open. Expect LUV, B6, or both within a year.
Will somebody else turn it into a hub? Probably not. Could I see LUV running 100 flights/day? Yep. That, plus the natural bump in service from all the other big carriers will be much better for the businesses in the greater PIT area, as their cost of travel will drop thru the floor.
If you search this forum for posts on PIT, this article re-affirms that which I've been saying for months: US needs PIT a lot worse than PIT needs US, and the area will probably be better off without a monopoly hub.