Just wait a year, cree's will be "old" by then!
One thing though is that eventually, efficiency will approach a physical limit since you can't get more energy out (in the form of light) than you put in (in the form of electricity). Right now the Cree emitters are about a quarter of the maximum theoretical efficiency for a white light source based on some estimates I've seen thrown around on these boards before. With a green light source -- since the eye is most sensitive to yellow/green light -- you could make a light even more efficient, but it won't be very useful. This is actually the reason why the yellow sodium lights are so efficient -- they put out a yellow (589 nanometer wavelength) that is very near the eye's peak sensitivity (555nm). However, those lights are totally unsuitable where color recognition is important.
However, as LED efficiency begins to approach a limit, LEDs will continue to improve in other ways -- including color rendering/light quality, and the ability to run single LEDs at higher power.
Another thing to consider is that Seoul Semiconductor (SSC) and Edison LEDs are both based on the Cree LED, so they have similar efficiency, but packaged different optics which gives them different properies. For example, the Seoul projects more light out to the side, so more light can be focused into a tight beam in lights that use reflectors.