The AMD CPU part is correct. However, as of now I would say that actually nothing is really futureproof.
Kaby Lake is just around the corner and those are the first CPUs to feature 4K video decoding. As 4K is the future, the next generation of Intel CPUs is the truly future proof one. Also, according to Intel's tick-tock-tock roadmap, the next generation will be the best of the 14nm manufacturing process. I highly suggest you wait for a 7700K and a Z270 motherboard.
However, if you do not want to wait for two more months, the best of the best you can get now is either the i5 6600K or i7 6700K. This is just my opinion, but to be futureproof, you have to have at least an overclockable CPU. I am using the i5 6400 now and it is already slowing down in the newest games even at just 1080p.
As you have mentioned that you want futureproofing on a budget and the only thing you will do with the CPU is game, I recommend the i5-6600K along with the ASUS Z170-A. That is your best option for now, and it will set you back around $400.