https://us.forums.blizzard.com/en/wow/t/imagine-your-progress-being-deleted/835519/75
Here, let me do it for you - Rozen already linked the quote in particular and it specifically states they were joking about it. That is literally the sole “museum” reference. They have said a number of times they wanted to provide that experience, but nothing is ever set in stone - Blizzcon has announced specific details that never make it to fruition, or are changed later anyway.
Blizzard isn’t going to have all the current Classic realms sitting active but dead. It’s just not feasible.
So you would rather play on a dead realm among a dozen Classic-only realms while TBC realms thrive, than move to a designated Classic-only realm to play with people who think like you do.
Burn the ship rather than take a lifeboat.