was going to say the same thing. All this talk of 'hypocrisy' holds no water.
By the time Cap 3 comes out, Cap would have had 2 solo movies and IM will have 3. Plus they would have appeared together in 2 Avengers movies in a cinematic universe that is 13 movies deep. Plus, lets not forget they already bumped heads in Avengers 1 so the precedent has already been set. We dont know whats going to happen in AOU but i'm guessing they're going to clash again and lay the groundwork for Cap 3.
The point is this, IM and Cap are have been fully fleshed out and characterized over 7 movies. the audience knows everything about these characters: their origins, their psyches and what their stands on various issues are. Even though its not the route i would have taken, having IM in Cap 3 is a lot more of an organic progression than than Batman in an MOS sequel. These two situations are nowhere near the same thing.