A question:
Will TW3 make use of multiple core CPU's? Since most games don't really need 4 core cpu, would it be overkill to go for a even higher number of cores then that?
Here's the thing, there's quite a difference between "needing" and "wanting" something. You're right that most games these days don't "need" a quad core CPU. In other words, they can still run on a dual core.. But for quite some time, quad cores have been offering a
MASSIVE performance increase over their dual core counterparts in modern games.
Every single current gen game engine can make good use of a quad core CPU. And the most licensed engines (and some in house ones) can make good use of 6 core CPU. Frostbite 3, CryEngine, AnvilNext, Unreal Engine 4, basically all of the big premier engines. Games that scale well above four threads, usually have the rendering working across multiple threads for extra performance.
Now according to what CDPR has said about Red Engine 3, and even based on precedent (Witcher 2 could use a quad core CPU and that was a DX9 game), it's safe to assume that the Witcher 3 will take great advantage of quad core CPUs, and even more, hyperthreaded quad core CPUs or even hex cores!