That point was when Minecraft was worthless. It's currently somewhere around the $2.5b mark in value. But that's just splitting hairs, it won't likely ever be open-sourced after MS acquired it.

That said, they also promised a modding API too...

What he actually said was "Once sales start dying and a minimum time has passed, I will release the game source code as some kind of open source." [0]. Sales haven't died down and he doesn't own it anymore anyway.

[0] http://web.archive.org/web/20100301103851/http://www.minecra...