Depending on the action and set pieces, BP2 actually has a strong chance of matching BP1's box office. It just wouldn't be the same split between domestic vs foreign.
700 million domestic is upper echelon in the USA, so that is tough to replicate. Not even Infinity War could do that.
However, 645 million internationally... while that's higher than 80%* of MCU movies and 100% of DC movies, numerous films like Skyfall, Frozen, Jurassic World, Fast & Furious 7 & 8, etc have grossed 800 million to 1 billion overseas. *For reference, Iron Man 3 did 805m foreign and CA:Civil War did 745m.
BP may have capped out it's domestic potential, but it has untapped dollars in it's international markets depending on the improved cgi, set pieces, and action (i.e. what foreign markets seem to cream their pants over). Not that it needs to match or exceed BP1. I mean, if
only grossing 1 billion is seen as a moral victory for haters, then cotdamn BP fans are the real champs