There's quite a bit of that in this series. Wesker teasing Steve would come back as he did. I still think he's alive for some reason. Billy isn't dead. Neither is Carlos.
I do kinda wanna see a B team game of the supporting cast returning.
Every Outbreak character was great, especially comparing to the dogshit Resistance characters and I think it's inevitable for them to revisit Outbreak or make a new one since it's fanbase is growing with even the biggest streamers asking for it.
Billy - Probably went to hiding and could have gotten a new identity. Sadly, he is still pinned for crimes he didnt do and as far as we know, his innocence was never proven (You'd think Rebecca would dedicate some time post R.C or post Umbrella's fault to prove his innocence). Either way, its unlikely he will ever return, at least without some retcons thrown in the way.
Carlos- Iirc, the last thing he did in canon was share a drink with Jill, to celebrate their survival and they parted ways. Carlos is a mercenary, he works for the highest bidder so its unlikely he would join the BSAA or anything of the sorts. There is also the fact that anything associated with Umbrella would be investigated and that counts the group he was part of so he no doubt thinks its best he lay low while this whole Umbrella's fall stuff is going on. Still, I wont discard the possibility he could do jobs for the BSAA if the price is right.
Steve- Maybe they intended on bringing him back at some point. And it would make sense Wesker would be involved. I cant even discard the possibility that Jill's role in RE5 could have been Steve's tho it wouldnt have much impact without Claire being Chris's partner. But Im just speculating because outside of teases, Steve still remains very much dead. However, if Capcom ever makes a C.V remake, I wouldnt put it above them adding some scene that tease Steve could still make a return (maybe for RE9/10 or something).
As for the other B-team characters we have maybe Ashley, Sheeva and most of the RE6 cast to be honest.
Ashley- Forget about her ever returning. Nuff said
Sheeva- Outside of a RE5 remake, it wouldnt make sense for her to return either way as most of the series takes place in America or Europe and Sheeva is part of the Africa Chapter of the BSAA so there isnt much plot reason for her to get involved unless it affects that corner of the world. It is still implied she and Chris keep in contact tho so never say never I guess, Im honestly surprised she didnt appear in one of those CG movies/series, especially if Capcom would want to "diversify" the cast.
Sherry/Jake/ Leon's lady partner I cant remember the name and I dont care to check- Capcom is really trying to avoid anything RE6 related as much as they can. Even after 2 whole entries, we havent got any sort of connection to RE6, almost to the point you could almost argue that its in a "canon void" where it is canon because it cant be uncanon so the best thing they can do is never reference it ever again and its characters are the sacrificial lambs so its unlikely we are seeing these three ever again...especially Jake and Leon's lady Partner. I could maybe see them making an exception for Sherry, we will see.
There are many many others but I was just focusing on the main entries.