The 1060 being constant, there would be some difference between a dual core and a quad core. Games Like GTA IV and V, Doom, Witcher 3 and Crysis benefit considerably from a quad core. Upcoming AAA titles will favor quad cores more and more.
It is always better to invest in a 7th Gen quad core over a dual core as you want to play latest AAA titles. Now you wont be bottle-necked to the point where you would see a sizeable difference, but expect to see a 15-20% difference in some latest games. The gap is only going to get bigger in the future.
Ex-i3 gets 78 FPS in a Battlefield 1 benchmark, while the 115 FPS is what the i5 gets you. Now as long as you are getting above 70 FPS , you would not mind, but at higher resolution and with Ultra HD in picture, you would want to get a quad core as a long term investment.