Total War: Warhammer 2 just got a release date announced: September 28th, 2017. It was certainly a lot faster than I thought, but no complaints from me.
The races that were already announced were Lizardmen, High Elves, and Dark Elves. The unannounced race is most likely Skaven, due to some observant users on the r/totalwar subreddit:
I plan to add write a Wood Elf army and/or campaign guide before the release if time permits. I have been busy lately with various creative projects and work. I’ve also been putting in some time on Von Cartstein campaign but I find Vampire Counts armies to be fun sometimes, boring other times.
For those interested in multiplayer army compositions, I recommend Ninjahund’s list of popular builds in the current patch/meta here.