Parmandur
Book-Friend
I believe Dark Sun material is still possible this year, but that depends entirely on how the next round of Mystic/Psion testing does. An updated UA could drop next month, and if it's really good, could pave the way for a November release. However, they'd still need to playtest some defiling and a few races.
The comments Perkins made about people who liked CoS and his 2020 AP made me think he could be playing in another setting. Mayhaps that Spelljammer/Planescape AP that starts in Lantan, either dealing with Gith vs Illithids, of that Great Modron March.
A second Xanathar style book should easily be happening this year with WotC ramping up on subclass UAs. Unless, they are going in a surprise setting book!
The adventure compilation that Welch is spearheading is a sure thing, but I'm really curious about the overal theme of the adventures, if there even is one.
My wild card prediction: 5E Modern.
I'd looooove an Urban Arcana Setting book.