It's probably very smart of Notch to retain what he can regarding the Minecraft IP. What a lot of people seem to miss is that Minecraft isn't only about the "official" game.

It's a platform for development. More importantly, it's a platform that lets many people create things in 3D without having to bother with OpenGL/etc.

If you think I'm talking about pixel art or other static things, or if you think I'm talking about mods, I suggest watching these, which are all stock minecraft only.

* SimCity reimplemented in vanilla redstone & in-game command blocks *

http://www.jigarbov.net/simburbia-map-release/

* FVDisco's Cake Defense, a wave-attack game with many features. (everything FVDisco has done is outstanding...) *

https://www.youtube.com/watch?v=OwxD3axvgt4

* Razul, an older scripted rpg adventure game with command-block based quest system *

http://www.planetminecraft.com/project/razul---skyrim-inspir...

* Hypixel, a many-thousand player custom server that works with the stock client *

https://www.youtube.com/watch?v=k1BdSq8fMtY

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The larger ideas that Minecraft is effectively a prototype for is basically the VR environments we've wished for over the last several decades. We achieved a lot of the 3D graphics capability (and are ok with sound, the few cases where the developer bothers), but interactivity is just as important for immersion. Not being able to interact with things that are not part of the "intended" experience can rip you right out of your suspension of disbelief.

This interactivity is what Minecraft gets right, and we've barely scratched the surface.

Minecraft : interactive 3D voxel games :: NCSA Mosaic : hypertext documents