The future
I plan on developing Minecraft until it's a finished complete game, with a downloadable client (with fullscreen mode), custom key re mappings and possibly modding support.
For as long as people enjoy and purchase the game, I will develop extensions after the game is done.
Once sales start dying and a minimum time has passed, I will release the game source code as some kind of open source. I'm not very happy with the draconian nature of (L)GPL, nor do I believe the other licenses have much merit other than to boost the egos of the original authors, so I might just possibly release it all as public domain.