Recent speculation has suggested that the Sentry will debut in Marvel Studios' Thunderbolts, and the newest rumored casting has been imagined in stunning MCU fan art. Marvel Studios chief Kevin Feige announced the development of Thunderbolts in 2022, revealing the team's first line-up to include Yelena Belova, Bucky Barnes, Red Guardian, Ghost, Taskmaster, US Agent, and Contessa Valentina Allegra de Fontaine, in the Avengers-style crossover project since 2019's Avengers: Endgame. The storyline for Marvel Studios' Thunderbolts in Phase 6 is currently unclear, but many have speculated about the involvement of one of Marvel Comics' most powerful heroes, Robert Reynolds' Sentry, which could seriously alter the status quo of the MCU.
https://screenrant.com/mcu-sentry-phase-6-mystery-character-art/