Thank you noting that because I was just like 'Wait. How will they manage another game when Minecraft is still in Alpha stadium?'
I mean, Minecraft is a very interesting game as it is, but I'd guess that most people pre-purchasing it (and it is still offered under that description) expect it to be developed further, and probably count(ed) on a sizable share of their money being used towards further development...
(but good to hear that Notch is still working on it)