Crytek's Roman-era punch-'em-up Ryse and Microsoft's own next-gen Forza are both rumoured to be launch titles for the putative and unconfirmed (but daft if it doesn't happen) next generation Xbox (itself rumoured to be announced at the end of May.)
Ryse, formerly known as Codename: Kingdoms was announced back at E3 2011 and featured hack and slash combat with deep Kinect integration. The team has gone quiet on the project since then, though it's still heavily-featured on Crytek's 'Games' pages.
In June last year, Joystiq spoke about Ryse to Phil Spencer at Microsoft Studios who said ""We're just not at a point right now to show the game, and instead of ... we're still working with Crytek, we're still extremely committed to the relationship, but we want to make sure that we're putting our best foot forward every time we show the game," Spencer said. "You'll see more about that game, no doubt." The project was rumoured to have shipped from Crytek Buadpest to Crytek Frankfurt at that time.
Details on the other three games are light on the ground. A "Super life-like" Forza is promised, alongside a zombie game (to go head-to-head with ZombieU perhaps) and a family game set on an island with Pixar-quality graphics.
Thanks to the Verge for spreading the totally-unconfirmed-rumours.