I bet they’ll follow the comics introduction of Sentry.

I dunno how to spoiler tag, but I’m gonna try…

!Apparently Sentry shows up in Thunderbolts. The F4 movie being set in the 60s would follow along with his comic introduction (which admittedly is kinda corny) where he was there all along, but the F4 erased him from people’s memories.!<

But they’ve already done that with Spider-Man, so maybe not.

Edit: I failed.