I think the general thought is that if Universal gets Sky, they will then want to buy the final 39% of Sky from Disney (obtained in the Fox deal). It could become a bargaining chip for Universal to get the rest of Sky (possibly), which they definitely want more than the Marvel theme park rights. Problem is, it is not Disney's priority to get those rights, and Universal will likely think it is worth more to Disney than Disney is willing to factor in. But some more knowledgeable than me do think that this could possibly happen because it just becomes a way for Universal to sweeten a deal (basically have to pay less for that portion of sky without parting with something really worth too much to them). Obviously there are going to be some fans that disagree with it not being worth that much, but when it comes to this sky deal, it is very small potatoes, which is actually the only reason it might actually work.
But this assumes Universal wins the sky sweepstakes (Disney has not given up yet). A part of me hopes that Disney's end game is just to get Universal to pay too much for Sky. I hope the bidding war continues, as if it does, the price Universal would have to pay to Disney for Sky would go up (two great outcomes out of this -- one is that it will increase the small chances they get the Marvel rights, and two - it will lesson any negative short term impact the Fox contract has on WDW).
I personally believe that overall the fox contract will have a positive impact LONG TERM on Disney, but it could have some negative impact short term. That's why I am rooting for a bidding war that Universal wins for Sky. Disney gets Fox and they lesson how much it cost to get it. Despite what many want to admit, Disney is really good at getting value out of things they get. It just often times has short term drawbacks.
There is some people who believe that it's possible (perhaps not legally) that Disney and Universal have had some backroom talks regarding the Sky bidding war -- perhaps Universal could use the marvel rights to "encourage" Disney to stop a continued bidding war. There is a lot of reasons that Universal would want Disney to stop...I just don't think Disney would have enough motivation to risk having "backroom" talks.