How to progress Classic WoW without repeating the past is a difficult question. Guild Wars 2 may hold some answers regarding how to add content without raising the level cap.
Certainly donāt want to see homogenization of the classes happen again. Keep the RPG in MMORPG! Keep things unbalanced; rock, paper, scissor classes if need be, just donāt homogenize them.
Separate timeline/universe is probably a great idea. Keeps players interested in both Retail and Classic, at least on the surface.
Donāt let Cataclysm happen again, it was out of nowhere to begin with and erased old Azeroth, which is one of the main reasons they resurrected it with Classic, I imagine. You can still bring in the new zones since Blizz already has those assets.
Focus more and expand tradeskiling. Make it unavoidably necessary to the game and economy!
Maybe make LFD/LFR only available when you are standing at that particular meeting stone for that dungeon raid?
Garrisons were fun, IMO, but isolated us all. Figure this issue out. Maybe use layers with many people in a āGarrison of a particular configurationā if we get there again, none of the individual phase garbage. Housing is something that has always been missing from WoW, yet in many games before and after. Figure it out Blizz!
I donāt have any good answers, really, not right now. But I did want to spitball the idea of a Retail vs Classic BG. Man, talk about a smacktalking opportunity! Probably a balancing nightmare, but whatever, the idea is fun to think about.