Seriously, by the time Cap, and the Avengers will have come out, we will have had 5 different marvel franchises all tied together. This will be THE cinematic Marvel universe... F4 will seem like a distant "What if?" film by then....
Seriously, think about 5 years in the future... Marvel have already said there are going to be other movies after avengers, including maybe Dr Strange, Luke Cage, Namor etc... that will lead to roughly 10 franchises all floating around, and all crossed over and related to one another... Fox and Sony will find themselves in a tight spot, because no one will consider their films as serious parts of the marvel universe. I honestly wouldnt be surprised if somewhere down the line they make a deal with marvel to combine the franchises, especially now that Disney could help them afford it.