If its just gaming a Core i7 6700K should be enough,but X99 does have advantages for other stuff though.
Regarding the card,apparently the GTX1080TI launches next year at CES 2017.
But the question is do you need one?? Unless we know what resolution and what games you play,something like a GTX1070 probably would be fine for most games at 1080P and 1440P
IMHO. Even at 4K,the Pascal Titan does OK,but how long it will continue to do so is debatable as more intensive games get launched in the next 12 to 18 months,meaning you might need to consider getting another card over that period to run in SLI.
Looking at how much the GTX1080 and the Pascal Titan costs,it probably means £700+ I suspect,and the last few cards like the GTX780TI and GTX980TI have been replaced in a year by faster and cheaper cards.
So unless you really intend to push the card,it might make more sense to do more frequent but "cheaper" upgrades to your graphics cards. CPUs,etc tend to much more longer lived from experience!!