Cheers for the answers, had been wondering/worrying about this as well, as my good ol' reference GTX 690 (I know, it's a mini-nuclear reactor in terms of heat generation) is reaching silly temperatures, even for it (peaks to 90/86°C at times in FO4, lingers at 82/80°C most of the time), and had been pondering if I should upgrade once the GTX 1080 comes about.
Just to clarify, though, what if the i7 2600k wasn't overclocked, but at it's standard 3.8Ghz, would it bottleneck a GTX 1080 notably then?