Downey, Evans and Ruffalo are gone so no IM, CA and Hulk. Helmsworth says he will do another Thor movie but I doubt he will still be around for the next Avenger movie whenever it premieres. Cumberbatch is a maybe. Johansson will do her solo movies and will probably be out as well as Renner. I think Rudd will out after the next Ant Man as well.
That leaves Captain Marvell, Black Panther, Spider-man definite probably also Shang Chi. Maybes Dr. Strange, Vision, Scarlet Witch.