Do you already have the GPU, or you are planning to upgrade ? Which GPU are you currently using ? On 1080p, you should be fine, IMO. But which CPU are you having ? With regards to the future proof, it will actually depend on the type of game being played, and the graphics/video settings applied. But no GPU/system is future proof though.
Some games are CPU-intensive, and some rely on a powerful GPU. GTX 1080 still offers a very nice performance though. I honestly don't think you should be running into any serious issue at least on 1080p, though others can correct me if I'm wrong
Are you planning to buy a NEW card, or second hand ? If the price is Okay, and you cannot wait, then go for the GTX 1080.
But my suggestion would be to WAIT for next-gen GPUs to arrive, be it from AMD or NVidia. NAVI is just around the corner, though it would "mainstream". Or better yet, grab one of the latest TURING arch GPUs. The GTX 1080 is one generation old, and Nvidia has already launched their new TURING lineup of GPUs, both in RTX and GTX segment.
One more thing. Next-gen consoles are arriving this year, and as per rumors, the hardware requirements for games are going to get a lot steeper, at least on the CPU side. When consoles start offering a more than 2 times the boost in CPU performance, you can bet that gaming PCs will be put under strain once AAA titles start making full use of the new hardware. It will also force developers to adopt low-level graphical APIs and further focus on multi-threading and CPU optimisation.