Everyone he talked to said he would never need more then a 1060 to game.
It comes down to their definition of "need".
1060 will play just about everything out there at good settings....right now.
1080 will play everything at maxed out settings and is future proof for a few years.
Right now with a 1060 there's a few graphics intensive games he might have to set to medium settings. In 2 years he'll be having to turn most new games down to medium graphics settings.
1070 that he got is a great card though that is very future proof too.