I'm going to go with single 1060 here for support etc. SLI doesn't scale perfectly as it is, and, a GTX 960 on paper is half of a GTX 980.
I'm LITERALLY the worlds' first person to take a GTX 980 home and I still own it. Tomorrow I'm getting my GTX 1060 Max Q laptop; I plan on benching things about as evenly as I can (same res, RAM, same CPU core and frequency) and I'll probably post results to this group