I just reread my earlier post and don't know why the fuck I mentioned fable. I think it was a random thought from the "biggest commercial success" thing. Sometimes the biggest successes are only so from being so hyped up
For some reason I don't think WoW is going to have people running 5 year subscriptions. Granted, it'll last for 5 years and more as long as the main attraction of the BGs aren't utterly retarded in implementation. But the same account for 5 devoutly paid every month...mmm, doubt it. No MMO will have EverQuest's godly retention rate, not even Vanguard; the playing field just isn't the same anymore.
Blizzard is probably making out like bandits right now, though, moneywise. No argument.