I love the sound of Unification III, and it makes perfect sense, studio-wise. The Cage "sequel" in S2 was well received and I seem to remember fans being pleased that the original footage was included as the previously on. Obviously, the studio would be keen to try to repeat that with another "legacy" episode, and of course Michael is going to want to try to find out what happened to her little brother over his long life. Depending on what components of the Angel suit are still working, Michael might have the magic television that her mother used to watch all through her life, so I'm guessing that in that year on her own, Michael's going to watch the in-universe equivalent of every episode of Star Trek on Suitflix, and she'll know where he ended up and how he lived. Of course, there's an opportunity there for us to find out that Picard's 20 year programmed lifespan got "broken" and Synth Picard might show up in a network of caves to offer Burnham a Spock themed mind meld ("I'm looking for Captain Picard" (dramatic pause and a figure walks out of the shadows. "And you have found him, Commander Burnham".... Sweet Baby Yoda, I hope that doesn't happen). I'm expecting/hoping that by the end of the season, the Disco crew will be time travelling back in time to a point when they can prevent the Burn from happening, and possibly that time frame is the Sanctuary, although I'd prefer the Sanctuary to end up being DS9, with the Bajoran wormhole being the only quick way out of the effects of the Burn. It would make sense that DS9 would become a destination people would dream of getting to in order to skip over to the Gamma Quadrant and back to warp life. Of course, a thing will happen, a butterfly will get stepped on, or the Time Police will show up, something setting S4 off in a completely different direction, and maybe show us a pre-Burn Golden Age Federation, with the uber-advanced station and ships seen in the debris field in the trailer.
I'd also love to meet Dax again, and I'd be ok if our new Trill crew member ends up being the latest host for Dax. There's been more than enough time for new backstory for the character to make it fresh, DS9 would be many hosts ago and the Dax lineage would be much longer.
I'm really looking forward to S3, I think the jump forward is an excellent idea. Time crystals have been in the opening credits since the beginning, so I'm hopeful that each season of Discovery will be set in a different era/universe/version of Trek, and before the end of it's run it will have given us a fresh look at the Star Trek timeline now that we have the technology to really visualize it on the screen in a way Roddenberry would always have loved to, but never was able to.