I was actually thinking about this the other day as well.
I'm not 100% that Disney owning Fox will end up with any of their horror properties pulled from HHN.
Let's be honest, Disney is not going to make any use of many of their newly acquired horror properties in their parks (American Horror Story will not be at Not So Scary for instance). So, why wouldn't they keep licensing them out for UNI to use?
Sure, it could be viewed that they wouldn't want to give "the competition" any leverage; but, it would still be a promotional vehicle for the property. Kind of win-win if you ask me.