No one knows when 9th gen is even coming out, as there is no real competition for 8th gen currently...
But, despite the added expense of a quality cooler (if your case is wide enough, a Noctua NH-D15 rocks), I'd likely spring for the 8700K, and if that is too expensive, might even consider the 8600K next. (CLock speed still plays a significant role in gaming performance at 1080P gaming)
Not sure when the next gen of Nvidia GPUs is arriving, only rumors currently, so the 1060 (6 gb) is a good 1080P card, and the 1070 is a great 1440P card....