I don't know about some of you, but if this is true, it tells me a lot more things running in the background. If other rumors ring true, such as the "no used games," this makes a lot of sense. The running theory is that when bought new, the new 720/PS4 game will have a code to "tag" it as a piece of DLC, letting the user play it maybe without the original disc. If this content is accessable on the fly, more cores would be a necessity to run more programs, games and apps in the background. This could mean the new evolution of the Dashboard or the PlayStation's Xross Media Bar. With fewer loading in between everything and more accessability at the touch of the guide button, there might not be a need to have to be restricted to the main menu. It can all just be pre-loaded or running in the background at the same time.
On a side note, I heard someone mention this would be unlikely because of the pricing. The CPU and graphics card(s) the 720 is modeled after are priced together supposedly at "half a grand." Well... wasn't the PS3 exactly that much when it first came out? And the 360 Elite bundles just under that??