I have to believe eventually something will make Disney want to buy out the contract. When it happens it will most likely be part of some deal between Disney and Comcast concerning something else. The two companies work together so much on so many fronts, it's bound to eventually happen.
Look at the deal they made trading the rights to Oswald the Lucky Rabbit for Al Michaels announcing contract. I could see something similar with the Marvel rights and ESPN or one of the other cable properties Disney may be looking to unload. If both parties find something they want, it could happen.
Also, Disney will want to have more of the Marvel attractions developed for the other (non Orlando) parks and then be able to more cheaply clone them for here.