Josh Brolin’s Thanos is set to appear in at least two more Marvel Studios films before starring in Avengers: Infinity War: Pt. 1 and Avengers: Infinity War Pt.2.
In an interview with Nuke The Fridge, the actor revealed that he’ll somehow work on Thanos both in 2016 and 2017. When asked about his future plans for the character, he responded:
“The fact that it’s so, it’s like, Yeah in 2016 and ’17, what am I going to be doing? Oh, I’m going to be doing that. I’m very lucky in that way, man. I just get presented these things and I go wow, really? Why now and why this? The possibilities for Thanos are unlimited.”
Within those two years, Marvel will release Captain America: Civil War, Doctor Strange, Guardians of the Galaxy 2, Thor: Ragnarok, and Black Panther. It’s hard to tell however, if Brolin’s comments mean that he’ll be filming Marvel movies in those two years, or if those two years contain releases with him in them. Out of the four films releasing in those two years, Guardians of the Galaxy 2 and Thor: Ragnarok seem like the most obvious candidates. Guardians 2 is almost a guarantee, with Gamora and Nebula—Thanos’ daughters—returning to the sequel. Thor, meanwhile, could easily shift itself deeper into Marvel’s cosmic realm and somehow include Thanos.
However, if Brolin is only referring to 2016 and 2017 as years that he's filming, one of the projects would have to be Avengers: Infinity War, which opens in 2018. Either way, any more of the Mad Titan between now and Infinity War is a good thing.