I still think that Thor Ragnarok is gonna have very good reviews and will most likely be maxing out around the 850M mark in terms of box office numbers. Toping that will be hard. Still, 850M would be very good... Thor The Dark World even being one of the weakest Marvel movies yet made 644M. Pretty much the same as the critically acclaimed Doctor Strange(673M) wich was a much more obscure character.
Thor has plenty of fans and the general public curiosity. Add to that a armored Hulk, a Hulk unleashed, that we have never seen before battling in a arena... Loki, the fan favorite... heavy hitters such as Anthony Hopkins as Odin, Cate Blanchett as Hela... plus Karl Urban, Tessa Thompson, Jeff Goldblum, Sam Neill... and then to top it off with Surtur, Fenris Wolf...
If it has good reviews and is critically acclaimed, and Taika Watiti's already has a few under his belt. Then this movie is gonna crush even more. 850M would be an immense haul. It would surpass movies such as GOTG, TWS... and would become one of the most profitable movies of Marvel history. Top 6 to be more precise.