It sounds like Avengers: Infinity War will be splitting its time pretty evenly between Earth and other planets. Infinity War is going to be a massive story with lots of moving parts and characters. It stands to reason that not every single one of these characters needs to leave Earth all at once, so while some go to other planets and get their teeth kicked in by Thanos, others will stay behind and hold the fort down. It's exciting to think of all the new environments we'll be seeing in the movie and it only reminds us of how massive the scope is for this movie.