I'm on the same boat so here i will leave my recommendation:
When the GTX 1060 and RX 480 i remember GTX 1060 beating it so far, but at today, AMD did a -awesome- driver job on their cards and the performance is almost the same (AT TODAY).
Differences are almost 5-7fps and the huge difference are in games which uses technology DX12 (Mainly when AMD did their homework, nvidia not yet).
So at today, both cards are a good choice to any user which wants to upgrade/pick their first GPU.
Now, lets talk about "future proof" (you said you want to play 4-5 years) well, sorry for said this but that doesn't exists. Mainly because we don't know which technology the companies are going to use, and also because you don't know if you in the future want to upgrade to higher resolution OR if your current CPU/mobo technology will bottleneck in the future.
Enjoy the today, pick any of both cards (Currently, some games uses more than 5GB of VRAM @ 1080p) they will do the job plenty fine.
Also, maybe on a year or two the card can get burned so there you have the future proof lol (happened to me with my Sapphire ATI 4670)
If i have the money now, in this moment, i would pick the GTX 1060 OR wait the RX 490. Why GTX 1060? Almost the drivers features. AMD did a really good job with their RX drivers update but, can they keep upgrading the performance with constantly drivers releases? At today, there is no noticeable driver release from nvidia which impacts in performance terms so, i would like to see that "head 2 head" performance.
i'm not saying at ALL RX 480 is not a good card, but i would not choose a card because it beats for 5-8fps in some benchmarks and some games. Period.
Happy chrismas! and ask again if you have still doublt about it.