Monthly active users for the entire suite of Blizzard games was ~37 million 6 months ago. That doesn't seem at all dismal to me. I'm not delusional enough to think that the majority of that is WoW, but to think that not even 1-2 million of that number is WoW is just as delusional, IMO.
Classic enthusiasts simply don't outnumber the number of Live players. I have no doubt it will be successful, but I find it extremely unlikely, and borderline blind zealotry for people who preach it, that Classic WoW is going to somehow out perform/ populate Live servers. What information is this assumption based on?