I would be so happy if they completely fixed, improved and updated Halo MCC, redo Halo CEA, maybe even add Reach and give Halo 3 a touch up. That would get a lot of good will and trust back. These aren't just disk games you can't patch, the technology is there to update but do Microsoft care about their biggest IP legacy. Hopefully.
I'd like to imagine a MCC update will hit with Scorpio to fix some stuff.
Now I dunno if they'll do that, but I think if Halo 6 isn't there on Day 1, something Halo related will be, cuz...yeah, it's Halo.