First off there would be different versions and servers for the game. Classic, Classic+, and TBC. Players who just want to play Classic can stick to classic only servers, Classic+ players can play through new content based off of the Vanilla style patch system post naxx ( Removing any chance at Expansions ), and finally TBC which is Classic with TBC expansion added. That way everyone is happy, people who just love Classic can play classic, people who love Classic but want more content get more content, and players who want to just right into TBC can go play TBC. Me personally I would love to keep playing all 3.
Classic+ seems to be a very interesting topic to cover. From all of the forum posts I have read there seems to be a lot of stuff people want added from expansions to enhance the game. In my point of view Classic+ would be a more simple version. Essentially Classic+ should continue off where Naxx left off, but instead of jumping into the Burning Crusade we would just have more content. In this case since we essentially traveled back in time there’s no telling what could happen, the Dark Portal could be destroyed instead and then we can move on from there. With Classic+ the first thing that comes to mind is just more patches with more content. Listed below is some of the content Classic+ could have.
- New Raids
- New 5, 10, and 20 man dungeons
- New world pvp events
- New quests
- New world events
- New reputation gains
- New gear for both pvp and pve
- New world bosses
So I think the best bet would be for Blizzard to follow their original patch based updates just without jumping into the expansions. There was a lot of content that was cut from the game such as karazhan crypts and Dungeon that was off the coast of Azshara. I am worried about Classic+ though, Blizzard would need to bring back some old school developers to bring the game back to it’s roots again and make Classic+ the most epic experience imaginable.