I think the best idea is ultimately custom servers.
The idea is that you can host any kind of server, with any kind of rules, on your own server.
People that like your map can “subscribe” to it. With enough subscribers certain perks become available, like free hosting from Blizz (ie. at 10,000 subscribers). You’d simply choose from list of servers, that would all be hosted by Blizz.
People can subscribe to your map even when it’s still in development, so if you get enough subs before you launch your server you could host it without ever paying a dime.
So why custom servers, then?
Well, as you all know, we all have different ideas for design direction for Classic. There’s no way we and Blizzard can agree to a direction that pleases everyone.
If Blizzard would design new content for Classic, they would once again do only PvE content (since it’s their most popular type of content).
People who have wanted another epic BG like AV since Vanilla, and improvements to AV, or even world PvP, would be left in the dust once again. And even from PvE point of view, I think some people might be tired of the raid formula.
What if you want randomly generated content? Well too bad, only thing retail devs seem capable of doing these days is pumping out raids and calling it a day.
Alot of live devs are also under a very different design philosophy. Im pretty sure they wouldn’t “get” Vanilla’s design philosophy, or they simply wouldn’t want to design for Classic in the first place (who can blame them - 15 year old game with a very specific niche appeal).
I, for one, wouldn’t want to have retail devs who feel forced to work on Classic even if they don’t want to, let alone having a burning deadline beneath their feet, set up by their higher ups (that would also probably bring us to the expansion model, though hopefully not).
Anyway, it’s best to approach Classic as niche product. Until someone can make a version of Classic that has lot of replayability proving it’s good business for Blizz.