Nobody is going to merge the two. It's like merging McDonalds and Burger King. Sure, they're in the same category and there are similarities but if both can make big bucks as independent brands, why would merging them make more money?
Obviously, it would make less money if there's any difference at all, so nobody is going to be motivated to do it. And why would Disney and Paramount even stop for one millisecond to consider such a thing? They're two rival companies. Corporations do work together, but only when there are big bucks as a motiation and that is hardly the case here.