I figure the PF1 classes will likely be brought over (at least ones not made obsolete by the new system, I suspect many of the hybrid classes will lose their reason to exist due to flexibility in the core classes). And I'd assume it'd be early in the design cycle. But I'd also guess there there will have to be a wait, maybe a year or two before we get them in PF2. Mostly because it's going to take time to design and test them to get something balanced and interesting instead of something just tossed together. And considering doing the many many classes in one go would be quite a bit, I suspect we'll get a few at a time. Maybe the APG classes plus Magus and Gunslinger in one book at Gencon 2020, Occult in another another year later then the hybrids that still make sense in a third.
I think we'll also need a pretty decent sized NPC/Monster/Villan codex. Preferably one of each, or more, and with more classes.
I personally would be thrilled to get a Pathfinder Unchained monster builder that covers non-core classes, but others will not be happy so it'll have to include ways to build them either way.
I also hope there's a PRD.
Thought of another possible hardcover: something that consolidates the various skill challenge rules. The chase rules, social combat, research at a library, exploring the wilderness, and anything else they can come up with that might require special considerations outside a general skill challenge ruleset. I hope the general framework is in the core book, but I also want a book that specializes in it and a bunch of class feats and spell powers that focus on that too.
Call it “Ultimate Exploration.” “Ultimate Downtime” can be the replacement for “Ultimate Campaign.”