One assumes they will UA two for each class, so we are due another sorcerer, bard, cleric, druid, ranger, artificer (I reckon the main motivation for doing the book now is to reprint the artificer for people who don't like Eberron). The rate of release seems to be stepped up - 2 at a time, 3 at a time, 4 at a time, suggesting the date of content lockdown is getting closer. But there is still quite a long time between content lockdown and publication. So my best guess is this book will come out in September, +/- 2 months.
Summer: Adventure Path (by Chris "If you liked Curse of Strahd, you'll like what I'm working on for 2020" Perkins)
S3 was recently published, under license, by Goodman's Games for their series of Original Adventures Reincarnated.Let's see … for the "Adventure Path," what classic adventure haven't they recycled yet?
My guess is an Expedition to the Barrier Peaks/Spelljammer crossover.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.