MCU Appearances to Date: Avengers, Avengers: Age of Ultron, Iron Man 3 (Cameo), Thor: Ragnarok, Team Thor (Uncredited)
Mark Ruffalo, like most of the core Avengers cast, signed a six picture deal when he joined the Marvel Cinematic Universe ahead of 2012's The Avengers. With a solo movie off the cards, the actor has only scratched the surface on his contract compared to his on-screen teammates. As cameos generally don't count towards contract fulfillment, Ruffalo has only appeared in three films thus far, meaning after Avengers: Infinity War, he'll still have two films to go. While the cast list for Avengers 4 is still up in the air, it seems all but certain the Hulk will return, leaving one film left on Ruffalo's contract.
MCU Appearances to Date: Thor, Thor: The Dark World, Thor: Ragnarok, Avengers, Avengers: Age of Ultron, Team Thor
Like Evans, Hemsworth has gone on record to say that following the filming of Avengers 4, his contract has been fulfilled. Unlike Evans, however, Hemsworth doesn't seem eager to say goodbye to Thor just yet, which is understandable given he's been playing this role since 2011.
Still, even with Hemsworth's contract finished, we still have two films left with his portrayal of Thor: Avengers: Infinity War and Avengers 4 -- which set photos have confirmed he'll appear in alongside Robert Downey Jr's Tony Stark.
MCU Appearances to Date: Iron Man 2, Avengers, Avengers: Age of Ultron, Captain America: The Winter Soldier, Captain America: Civil War
With a Black Widow movie -- finally! -- in the works, it would appear Johansson's time in the Marvel Cinematic Universe isn't over just yet. The actress has never outright stated how many movies she has left on her contract, only revealing that her contract has continually "morphed" throughout the years. It's thought that, like the others, she initially signed a six picture deal, which would be up with the still untitled Avengers 4.
Given that she's confirmed to have shot scenes with Brie Larson, she's pretty much confirmed for the Infinity War follow-up. However, with the news having hit earlier this year that Marvel Studios has hired a writer to pen a solo Black Widow movie, with Johansson working closely with the writer to flesh out the story, it appears her contract has been changed yet again. Until the fourth Avengers film hits next year, and we learn of Natasha's fate, it's hard to know if the planned solo film will be a one-off or a potential trilogy. If it's a one-off, Black Widow could mark the end of Johansson's run as the hero.