It's not just that. You'd get the likes of Mickey Mouse, Donald Duck etc potentially crossing paths with Bugs Bunny, Road Runner, Daffy Duck etc. It would be a virtual monopoly on cartoon characters too. And probably animated ones as well.
If that did somehow happen though, would the Marvel and DC universes be merged in the comics too?
And I don't see when Disney would have time to put out both Marvel and DC movies. Who would run it? Marvel? They have enough on their plate with the 3 movies a year which could easily go to 4 with the Fox characters under their banner now.