I personally don't think spending an extra $150 is worth it for "future proofing" a system. IMHO, in 1-2 years a 1060 will be "ok" for gaming at 1080p and getting 60 fps. You will probably have to lower some settings, but if you think about it, a 760 is still capable of decent fps in 1080p, with lowered settings and that card is now 2 generations old. And in 1-2 years when the new xx60 card comes out performing better than the 1070, rather than sitting on a $400 card, (more or less what you can get a 1070 for right now), you'll be using a $250 card, which will be a little easier to let go of to upgrade.
I was faced with the same decision, and that was the thought process that caused me to decide on the 1060. I'd rather go with the cheaper card now so I can feel better about upgrading when the next generation of graphics cards comes out, in addition to saving some money. I am also not too concerned with being able to play the newest titles on ultra at 60fps, I am perfectly content with lowering settings.
All this being said, I do think the 1070 is a better route to go if you don't plan on getting a new card when the next generation is released. If you look at the performance of the 970 now, it is almost on par with a 1060, and not really worth the upgrade. So using that as a reference point, you can kind of assume (future tech is hard to predict, so there is potential for error here) that the 1070 will be slightly less than the 1160, or whatever is the next xx60 card.