If we keep the comparison to "Big Bang I", then this is probably something like dedicated physix GFX or some SLI like what is posible with 790G chipset, where you have "master" GFX and "slave" GFX (Integrated GPU), but makes it possible to run SLI.
Big Bang II might be that this possibility is enabled with stand alone GFX of different kind, so that you no longer _must_ buy an identical GFX to the one you got, but you can just buy the newest generetion GFX, and make it run SLI together with your current (outdated) "top notch" GFX.

Would be nice to live out the old hype: "I buy a SLI MoBo, and a single nVidia GFX, and thus I just upgrate with another GFX when it is no longer enough with this one GFX, and put them in SLI." But not needing to buy an outdated GFX, but just buying another GFX from nVidia, and thus being able to run SLI.