I think in time, they will. Fox is about to turn the channel currently known as Fox Soccer to a new comedy-centric entertainment channel, FXX, and I wouldn't be surprised if they got broadcasting rights to the MacFarlane shows, King of the Hill, and Bob's Burgers and Futurama by 2015. It's less than two years away, and anything they feel that'll make FXX stronger, they'll do it.
For all we know, maybe FXX would put get those shows and only permit themselves to air it at certain times of the day, like how TBS doesn't air American Dad in primetime. My guess is that Adult Swim will keep some rights but dramatically limit their repeats of them throughout the week.
The winner in all of this will be Fox, whether they get cable syndication rights or not. If they do, it'll be prominent on bot FX and FXX. If they don't, they're going to get a truckload of money from Adult Swim allowing that network to keep it for another limited period.
What does the X stand for? It's definitely not Extreme. Extreme starts with E.