Okay I watched a few of those speculation videos now.
So fundamentally, for me, if the game is demanding a box price for "Classic+" it has to be more than a more polished version of Season of Discovery. Those WoW nerds are absolutely right that there is a demand for the progression gameplay loop visible in games like Palword and Valheim. Both were commercially very successful and lack the massively multiplayer aspect that has fallen out of game design for a long while now. Ignore the sandbox elements of those games. This is compounded by the success of Turtle WoW and Ascension which drew profitable player bases.
Now, all of that said they really can't just slap a new coat of paint on this and do something lazy like rebalance some talent trees. It has to break the Classic meta. As in the now hyperoptimized Classic gameplay we all know and love is just no longer a thing. No aggressive warrior stacking and so on. If they do not do that and still demand you pay a box price for the privilege then fuck them. If they just slap on a few extra zones, factions, etc and call it good fuck them.
Hoping for the best here but it might be a tall order for them to accomplish that. A true Classic+ would want to attract new players and not just the Classic Andys.
The basic bones for WOW are so good even now that you can absolutely build upon it.