Just to get an idea of what to potentially look to within the near and distant future:
Considering the fact that Rare is not developing Killer Instinct, Rare still has 1-2 projects in development considering they're a 2-3 team studio (Kinect Rivals being the only game they've announced and are developing). Lionhead has yet to announce a game for the XB1 and they're a 2-3 team studio. One of their teams is obviously working on Fable Anniversary though, but outside of their lesser Fable games which were done by the Kinect studios, they haven't released a game since 2010. We've yet to hear anything from Microsoft's new AAA studios, Microsoft Studios Victoria and Microsoft Studios Osaka. Crackdown is likely considering everything else on that Dashboard screenshot from the Xbox One unveiling has turned out to be an actual project, and with Spencer sporting the shirt on Jimmy Fallon, it's basically an ill kept secret at this point. Who it's being developed by is a complete mystery though, but hopefully it's a competent studio and not a shameless cash grab.
And from their smaller/Kinect/XBLA studios, we still don't know what Big Park, Good Science, Twisted Pixel (do they have a 2nd team?), Soho, Platform Next Studios, LIFT London, and Press Play (do they have a 2nd team?) are doing for Next Gen. Some of these, like LIFT London, are relatively new, so their games may or may not be ready for public consumption.
Undead Labs' (State of Decay) next game is probably a ways away from completion, but I personally can't wait for it. Certain Affinity (Halo Anniversary) and Playground Games (Forza Horizon? We know they're working on something Forza related for the One, so Horizon is likely) are some other 2nd party possibilities. And there's definitely more Gears of Wars to be had, since apparently Gears of War Judgement is supposed to be a trilogy:
There's obviously the chance for further 3rd party exclusives, and unforseen 2nd party offerings, but that's pretty much impossible to forsee.
