Oh man, the "It's not an MMO" bandwagon is growing!
I don't know what to think. On one hand, Koreans love the original Starcraft, which is an RTS. On the other, they also churn out MMO's, so I can assume they enjoy the latter as well. Would a MMO Starcraft cause a crack in the potential buyers userbase, dividing the RTS players from the Starcraft fans, or would it join the two in epic money?
The main reason it shouldn't be an MMO, however, is the fact that it could cut into the WoW userbase. Plus Blizzard themselves aren't bad developers, so they ought to know there are a ton of people out there that both enjoyed the previous games (me) and dislike MMO's (me again) and that a non MMO Starcraft would become the perfect complement to WoW: one attracts everyone but MMOers, the other attracts the rest.