Part of the issue with the current architecture is that information has to travel to several spots before it finally gets rendered for display. By putting the GPU & CPU on the same chip, you end up with a gain similar to what solid state drives gain over disk drives. The obvious issue is heat generation. If they make heat manageable, then putting them both on the chip allows for a pretty significant performance boost as you're not wasting as much time/resources moving the information from HD->Memory->CPU->Video Card->Etc...
WoW Blackhand-US-Date of Retirement: 9/21/2010... /Sigh
Devari - 90 Rogue 85 DK Druid/Mage/Warrior 70+
FFXI - Shiva "Retired.... Or not? One more try, honest."
Desmar - 65 Sam 36 Mnk 18 Thf 12 War
FFXIV - Devari Garamond - Sargatanas 50 Paladin / Culinarian / Weaver / Armorer
Beta - Devaria Ariadne - Ultros - Pugilist