1 Xbox exclusive in the first half of the year is par for the course. I also wouldn't doubt if they're holding back what would normally be Summer of Arcade games to release on their new console instead.
They've had way fewer exclusives versus their first few years, it's why I think it'd be better to get a PS3 at this point if you still wanted one of the two consoles, not unless you mainly want Halo/Gears or intend to get one of the older exclusives they have.
Though, yeah, it also could be an indication we'll be seeing their next console within a year. Or they just have yet to make some announcements, one of the two.
Most of the games are probably early 2013, and if they weren't rushing for launch they probably don't want to rush out a Wii U port. Still, I imagine there's potential for some of the releases later in the year like Dark Souls II, though that'll probably be PS3 or PC (or even both!) for me.