Quote from TheAstronomicalKidWhy do they need Minecraft 2? Minecraft is an unlimited potential. Minecraft receives updates. They would probably lose the player base they have now too. Why bother to make a sequel?
Nothing has unlimited potential, and this is all the more true if it is made with Java. Notch has said he would make Minecraft 2 at some point anyway (though he also said we would finish Scrolls first).
And why would the player base go away? The player base for CoD hasn't gone away, nor the player base for Madden.