I don't think people are necessarily tired of shooters. The problem is that, from the two franchises listed, Call of Duty and Halo, they are releasing games every year. COD does it all of the time, Halo was up to that point for four years I think. They did a great job killing momentum with that franchise when they dropped Halo 3, ODST, Wars and Reach all close to each other. I think they regained some momentum with Halo 4 and are moving back in a positive direction, but I don't follow it to the point where I know what sales numbers were.
Probably the best decision EA made was not bringing out a new Battlefield for this year. I remember seeing where they were looking to start doing that, possibly alternating yearly by bringing back Bad Company, but it was smart not to. If you play something every year, it's bound to lose it's luster at some point. Unless your game is the only way you can get your fix, like Madden or The Show. Or like World of Warcraft, where everyone in the MMO genre aspires to best that game but never comes close.