Max resolution for the 1060 is listed at 7680x4320@60Hz, so yes 4k is possible. It may not perform superbly in AH3 at that resolution, but I suspect it would do so very, very well. The 6GB memory limitation would hold it back somewhat, but the 980 is already limited to 4GB so it is better there, too.
The 1060 sounds great to me, especially considering the price.