I'm already on the MFT bandwagon as others, they already have a good selection of lenses already released, nothing too exciting that hasn't already been said. It is nice to see further releases from Schneider and Zeiss. Although ultimately, it won't be exciting until the next generations of cameras come around, hoping for further sensor improvements, the EM5 being the most fun of recent times, oh I must repeat, that hand grip is really nice!
APS-C sensor have the most development in terms of cameras and lenses. I guess most of the excitement is there, I'm talking about best balance of size, weight and costs here as the alternative to MFT. Larger sensors will always gather more spotlight and there's the major brands!