In the Avengers: Infinity War, Dr. Strange mentioned that he have seen approximately 14 million (14,000,605 to be exact) possibilities that could be played out. What if Avengers 4 starts from moment, when Dr.Strange siting on the rock and tell: "hmm, this is bad scenario, we need somethink better". Sounds silly, but Strange said, that there is one change to win Thanos, and then Thor loses oportunity, so that means Strange was wrong OR this reality is not the reality Strange told about. Ofc, avenger 4 could start with another scene, im talking about conception, that we saw some different timeline by a reasons. Also screen from trailer
This could be alternative reality with real Hulk in action and Captain Marvel somewhere.