It's long been known that Avengers: Age of Ultron would bring a change to the team's lineup.
With Captain America: Civil War on the horizon, though, and widespread rumors that Captain America will form "his own Avengers" independent of S.H.I.E.L.D. and Iron Man by the end of the film, one has to wonder: how radical a revamp are we looking at?
At various points in the trailer, we see Thor without his hammer; Hulk and Banner both seemingly disoriented; Black Widow saying that all things must end and just about everybody at Iron Man's throat at one point or another.
That "nothing lasts forever" was the kind of line that felt like a misdirect: trailer fodder to make things sound more dire than they really are. But...what if it isn't?
By the end of Age of Ultron, a number of characters will have been introduced to that Marvel Cinematic Universe who are longtime Avengers, at least some of whom have some loyalty to Captain America or conflict with Iron Man in their history. Is it possible, then, that following the events of the film, "The Avengers" could be comprised of Captain America, Quicksilver, Scarlet Witch, The Vision, Iron Patriot and Falcon?
(There's also the possibility of a cameo by somebody like Captain Marvel or Black Panther, of course, but that seems a bit more farfetched at this point.)
It's been speculated that adding in a few Avengers for Infinity War, Part One might give Marvel the chance to extend the deals on actors whose contracts expire after three Avengers films, keeping the recognizable faces around the franchise for a bit longer. Creating an entirely new Avengers team? That would certainly do it.
And it would also give them a chance to make Infinity War, Part Two -- with the presumptive addition of the Guardians of the Galaxy and the original Avengers reuniting after a few movies apart -- an absolutely epic film that nobody would dare miss.