Regardless of what happens, Avengers 4 will have a very interesting story to tell after the end of Infinity War.
A new rumor suggests that the still untitled Avengers 4 will be partly based on some interesting source material.
This means that Avengers 4 will at least begin 5 years after Infinity War.
It looks like they’re reliving the epic Battle of New York, which hints at some time travel trickery and some possible alternate timelines in Avengers 4.