Ummm there has to be a MK45. We know the Avengers are gonna get trashed by Ultron at least once in the movie. So he starts with MK43 since the MK42 was destroyed in IM3, he then uses MK44 Hulkbuster armor to fight the Hulk which we've seen in the trailers , so what else is he gonna use for the big climactic showdown against Ultron in the movies finale?? Fix his MK43 again?? Don't think so. And I'm sure the hulkbuster armor is gonna get ****ed up fighting the Hulk too. They're not gonna show everything in the trailers yet.... Hell we haven't seen Vision yet and we know he's in the movie right??