Not supported yet I'm afraid. But come Beta 2 on the 25th of this month they will be supporting multiple GPUs. Likely just DX12 unless new drivers are dropping for the game to support SLI/CF under DX11.
With the two dual-GPU cards your system will be an interesting test case to see how well it does. At the moment you are just running 1 of the 4 GPUs in your system. I'd be interested in an update from yourself once the next Beta is out, if you're willing. If it all works then you should be able to max out the game and have good FPS at 4K I would think. I don't know if they are yet able to "pool" the RAM in reality yet, though it is meant to be theoretically possible. I think that would make the difference of using 4GB or up to 16GB of VRAM for the game in your case. (As each of your cards is 2x4GB VRAM. Traditional SLI/CF will only allow you to use 4 as it duplicates the data across the VRAMs rather than being able to pool it together. That will be true even with your two cards which makes 2x(2x4), which should equal 16 but under DX11 still = 4.)
P.S. That is a beast of a gaming setup