Ubisoft Massive is perhaps not the highest profile studio under Ubisoft's wings as they've helped on the production of Assassin's Creed: Revelations and Far Cry 3 (multiplayer, co-op) in the last couple of years, but in the meantime they have been working on a major secret project of their own - a project that was always rumoured to be an MMORPG.
The most solid piece of evidence surfaced in Marc Cartwright's LinkedIn profile as he listed in his experience Game Designer on AAA Next-Gen Online RPG på Massive - A Ubisoft Studio.
Some sites have linked this information with the leaked images of something called Prince of Persia Zero, but rumours we've previously heard point in another direction. It was first thought Massive were working on a Tom Clancy MMO, but there is also the possibility of Massive working on an Assassin's Creed MMO - something that would surely make a lot of sense given that it's Ubisoft's biggest franchise (a Prince of Persia MMO makes very little sense). At this point, it's just pure speculation, but what we can pretty much be sure of is that Massive are working on a major MMORPG. The next gen part of it could possibly refer to consoles, or just simply "next gen PC".