Steady on now, this doesn’t mean a full-on sequel to Deus Ex: Human Revolution is happening. But it could mean that. Square Enix has taken out a trademark for Deus Ex: Human Defiance and that means … something.
Eidos Montreal (of DX: HR) fame most recently made the multiplayer bit for the new Tomb Raider, and are supposedly working on Thief 4 (though it’s gone all silent on that front, of late.) Rumours, as well as smart speculation, have suggested that the studio will have another crack at the series.
On the other hand, it could be a terrible free-to-play game for mobile phones. At this point, all there really is to look at is a corporation going “yes, I think we’ll put some sort of legal protection on this name, just in case.”