UPDATE: Crytek: "We don't comment on rumours and speculation."
According to the CV of one of the game's senior level designers, who has now left the company, it's an "X-Box Next Gen" project.
"Pushing boundaries of next generation gaming, RYSE is an original AAA IP from Crytek slated to deliver an Epic first-person melee experience in the Roman Empire."
A NeoGAF poster added further colour, explaining that a Crytek representative speaking at a recent CryEngine 3 student lecture had mentioned there was a "big chance of Ryse going next gen because of all the work they had to do and all the people they are hiring for the Ryse team."
We've approached both Crytek and publisher Microsoft Game Studios for comment and will update if any clarification is offered.
Sources recently told Eurogamer that Microsoft is working on a next-generation version of Kinect which packs considerably more power, potentially allowing the device to lip read players.