Yes, although in official Blizzard statements they haven't decided to do an expansion yet...it's hard to believe them. The plot has huge question marks left at the end, and World of Warcraft's plot is supposed to start four years after Warcraft III if memory serves.
As far as World of Warcraft fees are concerned, it is annoying to be required to pay so much, particularly after the 'client-for-free' experience I had with Shattered Galaxy. I am actually glad in a way, however, that they are going to be charging for continued use of World of Warcraft. The fee isn't going to be for the privilege to play the game. If it was about that, we'd have to pay for current battle.net games as well. The fees are there to support the development team primarily. The game is intended to continually evolve, have Gamemaster-run events, and to generally be better-run than anything currently out there. Also, the fees will go toward preventing those same 12-year olds you mentioned from hacking the game. It's a lot easier to get caught when your credit card number is involved and there are staff out there watching for hacks. Consider Diablo II, a game that despite Blizzard's efforts, has been utterly ruined by hackers and dupers. I'd love to see a Blizzard game that lacks that corrupting element. As far as whether World of Warcraft will be worth the price, I'll have to decide that as I go along.
I'm also wondering what you expected in the way of innovation from Warcraft III. I saw plenty of innovation in the game, though perhaps not in areas you were looking for them. One of the things that helped me realize this is playing other recently released RTS games. If you want to experience 'nothing new' there are some out there for you.