There's probably no MCU hero more worthy of a solo film than Black Widow. Scarlett Johansson originally only signed for Iron Man 2 and has been happily re-upping her contract ever since. Her quotes in Vanity Fair indicate that she is indeed departing the MCU after Avengers 4. Jeremy Renner's contract is also expected to conclude with Avengers 4 (his original contract called for a Hawkeye solo film that never materialized). Since Clint Barton is someone who has dejectedly spoken about how a guy with a bow and arrow is increasingly outmatched by the awesomely powered heroes and villains he now keeps company in, Hawkeye is probably finished in the MCU.
Mark Ruffalo, however, is believed to have one more MCU appearance scheduled despite Vanity Fair's claim that he is also finished after Avengers 4 - unless something changed in the interim (or that Iron Man 3 cameo really did count against the count).
OTHER POSSIBLE FINAL APPEARANCES
When it comes to later additions to Earth's Mightiest Heroes, things are more in flux. Paul Bettany (Vision) has been in the MCU since the beginning providing the voice of J.A.R.V.I.S. before taking on an android body and becoming a full-on Avenger in Age of Ultron. He doesn't have any appearances set after Avengers 3, and the same is true of on-screen love interest Elizabeth Olsen (Wanda Maximoff/Scarlet Witch); her contract reportedly ends with Avengers 3, and the actress has been coy about what comes next for Wanda. Also with an unknown future is Don Cheadle (James Rhodes/War Machine).
Finally, there's Samuel L. Jackson (Nick Fury), who has been working off a nine-picture deal in the MCU. He hasn't been making many appearances lately, but is set to appear in Captain Marvel before making perhaps his final stand as Fury in Avengers 4.
WHO'S STAYING IN THE MCU
Though it seems that a great many MCU all-stars are poised to depart the franchise, there are a number of heroes remaining to spearhead Phase 4, chief among them are the Guardians of the Galaxy. Guardians of the Galaxy, Vol. 3 premieres in 2020, a year after Avengers 4. However, Guardians' mastermind James Gunn has stated that Vol. 3 will mark the end of this iteration of the team, meaning that like the Avengers at the end of Age of Ultron, a new group will form to continue the franchise. Gunn is also masterminding the expansion of the cosmic side of the MCU.
However, since all of this happens after Avengers 4, Chris Pratt (Peter Quill/Star-Lord), Zoe Saldana (Gamora), Dave Bautista (Drax), Rocket (Bradley Cooper), Groot (Vin Diesel), and Mantis (Pom Klementieff) will still be the Guardians at the beginning of Phase 4 (assuming, of course, they all survive battling Thanos). Karen Gillan (Nebula) is a bit of a question mark, as her character's arc is more directly tied into big bad Thanos. Sylvester Stallone (Stakar Ogord) is also expected to return in Guardians 3.
The cosmic side of the MCU should continue to feature appearances from the immortals Jeff Goldblum (The Grandmaster) and Benicio Del Toro (The Collector). As for Tessa Thompson (Valkyrie), she made a huge splash in Thor: Ragnarok and is set to appear in Avengers 3 and 4. As she's also an immortal Asgardian and a popular new female Marvel heroine, Valkyrie feels likely to remain a key part of the plans for the cosmic MCU.
- Black Panther (2018) release date: Feb 16, 2018
- Avengers: Infinity War / The Avengers 3 (2018) release date: Apr 27, 2018
- Ant-Man & The Wasp (2018) release date: Jul 06, 2018
- Captain Marvel (2019) release date: Mar 08, 2019
- The Avengers 4 / Avengers: Endgame (2019) release date: Apr 26, 2019
- Spider-Man: Far From Home (2019) release date: Jul 05, 2019