2008 certainly means that some things will change in the graphics world. We believe that from this year on the future of graphics will be multi-core or multi-chip, depending on the approach.
ATI's R680, a graphics card with two RV670 chips, or Nvidia's soon to be announced D8E dual G92 card, are just the first step in this direction.
The next step is to put these two cores on the same die, the same way that the CPU industry decided to go about it.
The reasons are quite obvious and simple. Nvidia and ATI are getting close to a billion transistors at 128 Shader units with up to 800MHz core clock, and in the future, even with 45nm, it cannot get much better than that.
Therefore, you need two core graphics chips and that also means that eventually we might see quad core and octal core graphics chips; just give it some time.
That is why SLI and Crossfire drivers start to be incredibly important.