You know Minecraft is probably the best example to use for how long the gaming community is willing to wait or even pay for a half finished buggy game. It was a stroke of genius for Notch to sell copy's of the alpha for a reduced price to help fund the game and I believe this could be adapted to help developers make better games even with larger companies like SOE.
Minecraft has sold over a million copies now from what I've read. At 20-30 dollars a copy. That's not bad coin for a half finished title. Why aren't more developers doing this?
I don't need a release date (ever) if I can play the game now. I'll even pay full price for it and give you real time feedback on the features you add to help you make a game that won't suck.