I think Notch meant that the runaway success and "I'm a self made millionaire form this one bit of software, and it's not even finished!" was more of a one-off thing. Stuff like that is more or less "hit" based, some things become wildly popular but it doesn't mean similar things will be as successful and it almost always leads to the next big hit thing being something quite different from the last. I can't see this happening again for a similar minecraft style indie game for at least another decade. A different style indie game, sure.
The community funding model for indie game development is gaining a lot of tracking of late but it's also been around for quite some time.
<- Another Unity Engine game (scifi FPS) making good use of a similar business model.
You can play the game right on their website if you have the Unity web player plugin installed.