Edit: Notch has clarified his intentions for the immediate future in blog-wise fashion:
Last week, I participated in the 7dfps and made a hectic shooter greatly inspired by Doom, called Shambles, and it was some of the most fun programming I’ve done in many months. This is what I want to do. I want to do smaller games that can fail. I want to experiment and develop and think and tinker and tweak.
Well, YOU follow Minecraft. Marcus "Notch" Persson, having moved on from Minecraft development a year back, has been focusing on an ambitious space sim 0x10c. Except, not any more. We knew that back in April Notch had put the game "on ice", citing creative struggles. They don't seem to have gone away, and now - as spotted by US Gamer - he's told some people via a Team Fortress 2 livestream that he's given up entirely. But some fans plan to make it anyway.
And their response has been fast. The livestream comment was just over a week ago, and there's already a fan team put together working on the project. Which is impressive in itself, since the project was already so bewilderingly far-reaching. A sandbox space sim, with a ton of FTL elements, a pile of Elite, and ambitions to create the atmosphere of Firefly. When last seen it looked (and looked only - no sound) like this:
The fan project won't use any of Notch's code. Unless he decides to give it to them to surprise them, I guess. They don't even plan to use the same story. But they appear organised, with team leaders for each aspect of the game, and a desire to see whatever they imagined Notch's game was going to be come to life.
As for Persson, we don't yet know. He'd announced 0x10c in April 2012, so clearly put a year's work into it. Let's just hope he doesn't feel the pressure to equal or better then success of Minecraft with future projects, as that would stifle any chance of his getting anywhere.