Nvidia Graphics, Performance & Tweaking Guide.
Something to read until release perhaps. Lots of images as well

http://www.geforce.com/whats-new/guides/the-witcher-3-wild-hunt-graphics-performance-and-tweaking-guide

These numbers don't align with current benchmarks. Right now without hairworks the game runs at about 30fps on average on a GTX Titan X @ 4k ultra. How can Nvidia get over 50fps with hairworks on? Am I missing something?

They use dual GPU?

As the screenshot states Titan X SLI - and damn, they got some pretty nice scenes there.
Wish I could run the game it was meant to be played: at 4k