In my case it depends on its performance in Octane Render. If the rumors about OCabilty up to 2,4GHz are true and this actually transpires linearly as higher performance in Octane, then i guess i am buying 1080, preferably something like Evga Hybrid.
980Ti scores in OctaneBench 125 points (i assume on stock clocks with default boost). 1080 at 2,4Ghz should theoretically give 2x as much (since it has 2x FP32 performance), if in reality it scores at least 200, then its more or less acceptable. Its more than Titan Z after all.
If i however knew, that GP100/102 based Titan with 3840 cores will come at the end of the year for sure (and not a year from now), i would wait that half year.