It's nice that Valve is into PC gaming, but if the future is casual games and MMOs, it still indicates that PC gaming is in a very sorry state. It's not the sort of claim that counters the doom and gloom in a satisfying way for most of us. I want to play the triple A titles. I want to use a mouse and keyboard and mods.
Also, is Gabe Newell saying that WoW's success has been "invisible"? Everyone knows they make an unbelievable amount of money. I still don't see how it's a good thing for PC gaming in general, because everyone I know who plays it plays MMOs exclusively on the PC. If they play something else besides WoW, it's a new MMO of some sort. These days if you say "I'm a PC gamer" your response will probably be "Oh yeah, I play WoW too."