It won't do anything for exclusives on the 360, Halo 4 is likely the last first party game (apart from kinect) that will be released on the xbox 360. Then when Next gen comes it will be the same thing all over again - Halo/forza/gears/kinect.
That's why I am so much more excited for the next generation playstation, The amount of new ips and games just for the PS3 in it's later years is amazing and I can only dream of what's to come next, on the xbox side of things it seems they are going after casuals and sticking with what works without trying anything new.