Many of us who played since 2004 knew very well that neither tbc nor wotlk were as good as vanilla, in fact many believed that wow died with the release of wotlk and that it was a bad expansion despite the high numbers, wotlk added absolutely nothing of value to the game, ulduar is one of the best raids ever but that's about it, even ICC was mediocre, I personally wasn't impressed by it. By the end of wotlk, wow was at its knees. Now people no longer need to run to a private server to live again the vanilla experience, they instead go back to classic era. SOM is also pointless since classic era can already take care of these people, som would only have meaning if they added new features to vanilla that wouldn't break the game experience of course.
It's pointless to have a cataclysm release now, they should improve som instead. People really like vanilla.