Why Go Back To Congressional When You Have Philadelphia?

I never understood the AT&T National locking itself into Congressional for several years past the 2011 U.S. Open, and having seen just a bit of the event today at Aronimink, you have to think someone is wondering if they can get out of the contract and move the event to Philadelphia. Even if Anonimink doesn't want it on an annual basis, perhaps a rotation of classic designs in the area?