Personally, I would like vanilla to WOW TBC Gold remain the same and unaffected. It's certainly one of the greatest games ever developed and making any changes would likely ruin the overall experience.
There's no classic plus since retail is a thing. If project titan had been successful with its initial plans, warcraft would have gone out of existence long ago and we'd have been playing the successor to wow, since that's what overwatch was essentially to be.
But yeah, they won't be able to do something like a "classic plus" without the need to put retail to bed, as they would be doing original type of ideas for cheap Burning Crusade Classic Gold two distinct mmo's, that's far too chaotic