Two way SLI is still doing its thing. Three way SLI with the newer 10## series works also, but doesn't really return much for the cost. Microsoft has tried to model Windows 10 in a way that would allow you to use whatever you have. I'm not clear on whether games have to be programmed for that, so I don't think it's actually a thing yet. You see, DX12 is still very broken. Besides, DX11 is probably better for everything we use it for.
They must be disabling SLI because they have to in order to change system files, somehow? But, they could at least turn it back on.