I really don't think we'll see a solo Hulk movie (even if they had the rights) after the success of Ragnarok.Here are my predictions about Phase 4 of the Marvel Cinematic Universe. I've got a feeling Marvel will go back to releasing 3 movies a year in 2020. Especially since Doctor Strange 2 is rumoured to be released next year. Heck, they might even start releasing 4 films a year starting with 2021.
Black Widow(2020) - May 1st.
The Eternals(2020) - July 31st.
Doctor Strange 2(2020) - November 6th.
Black Panther 2(2021) - February 12th.
Guardians of the Galaxy Vol.3(2021) - May 7th.
Fantastic Four(2021) - August 18th.
Shang-Chi(2021) - November 5th.
Captain Marvel 2(2022) - February 18th.
Avengers: Secret Invasion(2022) -May 6
Spider-Man: Home for Graduation(2022) - July 29th.
Marvel's X-Men(2022) - November 9th.
The Incredible Hulk 2(2023) - March 15th(depending if Marvel gets the distribution rights to the Hulk back).
Avengers: Dark Reign(2023) - April 25th.
2 of the 2023 films will be part of a potential Phase 5.
Black Widow 2(2023) - July 5th.
Black Knight(2023) - November 22nd
I think Hulk is better relegated to team ups. Captain Marvel 2 would be a natural fit.