There is actually no features in the new expansion

[Astreon-sargeras]

Make retail classic+

Dear Blizzard here is what you do. In the next retail expansion, Do level squish to make LvL 120 —> LvL 60 There are people who want TBC, WotLK in the classic forum and some people who want Classic+. Listen to their ideas and implement them in the next WOW expansion. Make the next retail expansion feel like it’s classic+. If you do this, you can retain the classic players and those who want the new and improved version of the classic will go play the classic+.

I think this is probably why. They want to make the next expansion more like classic+, so that it will be the expansion both for the retail and the classic WOW. instead of keep inventing something new, I think they are gonna revisit old ideas and perfect them .