Malachore/Malacor, Ossus, and Korriban/Moraband are all in the canon now and some of the lore from the ancient era is also alluded to (like Ossus suffering some unnamed cataclysm). I'm hoping they further it by namedropping a few ancient/TOR era characters in episodes of Rebels, books, or the movies. While I'd like Sith Purebloods to become canon, I don't think it will happen. Thankfully the Massassai on Yavin 4 and their Sith connection exist in the new-canon, at least.
As far as I go, would love to see the ancient lords of the Sith like Ragnos and Sadow mentioned in some capacity. I'd rather they not get a samurai-overhaul like Bane did in TCW. But really, mostly interested for some Tales of the Jedi lore and characters to make it in. KJA is far from my favorite author of SW, but some of his stuff (and the coauthor's) introduced the groundwork for characters and scenarios that could really shine in a book or just reworked into the canon. Pssst, I want Exar Kun to be canon more than any other Old Republic era character. I'm holding out hope Luke's academy that failed in new-canon is still on Yavin 4, haha.
So - I want to see the Great Sith War And the Mandalorian Wars as canon, if just a footnote in a tie-in book.
And yeah, I guess they should add in Revan's arc and times in eventually because he's really popular (this is why Boba Fett isn't/wasn't dead and Darth Maul survived being cut in half, no?). It can't hurt. Revan getting mention with Kylo's background or him fascinated with Revan's journey would work well. Disney wants $ and Revan = $$.
No KotFE in the new canon please. It just isn't Star Wars enough. Kind of fun to play and I want to see the resolution on TOR, but I'll pass on having to endure it a second time, but Disney-fied. I'd prefer seeing a small bit about how Malgus did rise to become Emperor of a Sith empire, and then he was assassinated by traditionalists and the Sith were thrown into chaos (again). Anything but the Zakuul stuff in neo-canon.