Blizzard would need to get 1mill+ playing on past expansions to make it worth their time

and I highly doubt they'd get that after a couple months

Speculating on the kinda numbers they'd get is difficult-impossible right now. The Nost numbers are not helpful at all there.

Until Blizzard gives it a try or lets someone else give it a *real* try, it's dumb for anyone to claim that they know how many people would be willing to pay.