I think I get where you’re coming from OP and I agree with it in a lot of ways.
I never got into private servers mostly because I don’t like violating copyright laws, but part of it was knowing everything would get deleted at some point.
IMO it would be nice to have options for keeping characters on “Classic Vanilla” or moving them to “Classic TBC”. I plan to move to a “TBC Classic” with my main characters for my own reasons but would love to keep some alts on a static “Classic Vanilla” server. I completely understand that some people do not want to progress and the choice is good.
When TBC first came out it was exciting at first but it involved moving to the ugliest land possible (still) and then watch the servers guilds and community fall apart. It was so bad I just started again on another server. It sucked. I also have no interest in playing my original main on retail anymore. It’s still there but not the same at all, with 8 expansions everything is different.
So the point is yes it would be nice to have the option to just keep characters at 60 etc, even if it means moving servers, and not be forced to progress to another expansion or start fresh. A choice is really the best option for all. There are other people on these forums who feel this way and they’ve said so. What Blizzard will actually do is up in the air and I don’t really expect anything from them anymore. “Classic TBC” hasn’t even been announced (and yes I know the signs point to it).