The obvious followups include sequels to Strange, Ant-Man and the Wasp, Captain Marvel, and Black Panther and some potential new properties (i.e. Inhumans).
It’s possible Venom and Spidey movies going forward fall under Sony’s release schedule while still taking place within the Marvel Cinematic Universe.
Could the third 2019 film (the other two being Captain Marvel and Avengers: Infinity War Part 2) be another ensemble Captain America movie similar to how Civil War launched Phase 3?
With the end of a trilogy of phases so to are we seeing the conclusion of trilogies of starter Avengers.