Well depends on the resolution you are gaming at, and what you consider future proof. If you want to play at the bleeding edge of graphics there is no such thing. Will that rig run future games reasonably well, most likely yes. That is super overkill on your PSU if you aren't planning on running SLI/CF cards. If you are then it is an excellent one, I myself use it. No mention of a case or any other peripherals or if they aren't needed.
http://www.anandtech.com/bench/Product/288?vs=142 <---- That's the 2500K vs the 980X...down towards the bottom is the power consumption comparison. So ya, if the OP planed on running three of those cards and o/c on top of that...then I could see spending the extra $$ on an 850w psu.