Normally I don't get too excited about new versions of DirectX because they typically aren't as good as the promises. However early reviews of DX12 seem to indicate that there could be a 20% frame rate increase over DX11. One of the biggest changes is that DX12 will now take advantage of multicore CPUs. I believe that was something promised with DX11.
A project Cars developer recently said that DirectX 12 will provide a "30-40%" game performance boost on the Xbox. Followed by "I'm not exaggerating.". http://forum.projectcarsgame.com/showthread.php?27276-A-question-to-the-devs-about-the-frame-rate-issue&p=945141&viewfull=1#post945141
Anandtech did a DX12 mixed vendor GPU test a few months back and the results were rather surprising. Combining Fury with the 980Ti could get better results than pure SLi and Crossfire. Odd results from mixing older cards as well. http://www.anandtech.com/show/9740/directx-12-geforce-plus-radeon-mgpu-preview/4
This might be why Nvidia is rolling back support for SLi. If it works we might actually have a reason to consider low-end multi GPU systems vs a single highend GPUs. https://www.techpowerup.com/223923/...tx-12-multi-gpu-with-simple-abstraction-layer