I'd love to see them get classic vanilla up and what it was close to in 1.12.
But then, as mentioned in the video linked a few posts up, I'd love to see them add new content and go a different direction than TBC. A wow alternate, so to speak. Keep that vanilla dev team employed after they finish their work with a solid server of classic. Upgrade classic on a new server and get guildbanks in, better itemization for some classes. Get some specs to a viable limit. Add some more dungeons. Keep content hard, keep it so that you still need to pair up sometimes. I would absolutely live that!