But you really can't separate the stereotypes away from the roles. 'Seme' is a specific role that has certain tropes that go along with it, and the same goes for 'uke'. That's why I don't think anyone can say Steve's a seme or Tony's a uke because they don't fit those role.

I mean, I'm seriously wondering what J-fen is going to do when the movie opens up in Japan, because I totally expect some Avengers doujinshi out of it- but I have no idea who they will make the seme and will be the uke. J-fen already has the habit of uke-ifying any of RDJ's characters, but there's already a growing amount of uke!Steve fanart out there, so there's no telling who will end up in what role.