As Max (torchlight2) says, the market for PC games is really evolving. It’s generally-accepted in the industry that WoW will be the last successful monthly subscription MMORPG, and that future MMORPGs (including Blizzard’s own Project DiabloWikiTitan) will have to survive with various F2P financial models. Even non-MMORPGs, such as Torchlight 2, have had to adapt with smaller, faster, more efficient dev teams, that allow them to hit lower price points.
Blizzard may be the dinosaur in this changing industry, with the last big monthly fee game, and the last PC-only games that can sell enough copies to make a profit, and even then Blizzard is looking into new models, as we see in Diablo III’s real money auction house.