This right here.
Now, I'm not a business man, but if WWE is getting money from Fox for the TV deal, and Fox buys WWE, then Fox no longer has to pay WWE to air it's shows. It basically gets absorbed into whatever they pay WWE to buy them. They pay one sum in the buyout instead of (potentially more) over time with the TV deal.
It may not be the factor in a Fox buyout, but I can bet it's one of them when they discuss it with their investors.
That is if there is any truth to the rumors after all. I wouldn't bank on it.