It's really tough to find any recent benchmark info on PUBG that includes V64 using the same test system but, in regards to a GPU upgrade V64 to 5700XT you're looking at roughly 20-30% increase in FPS (judging by what I could find on 1080p ultra benchmarks). As far as all newer games being released, more and more seem to be scaling slightly better with more threads, but in the short term the 3600 with PBO/OC to ~4.2 seems keep up with the 3700x; no one can tell you how this will change a few months down the road.
At higher resolutions, like I mentioned earlier, the cpu is less of a bottleneck and therefor you're going to get a lot less out of a CPU upgrade at your resolution. So essentially any GPU upgrade will outweigh the CPU upgrade, but 5700XT vs V64, V64 is only ~26% slower so again not a massive step up. AIB cards might be enough to bring the 5700XT near parity with R7 which would be more like a 30-35% performance gap.
If all you do is game, and you're struggling to stay around your monitors refresh rate for avg FPS, I'd upgrade your GPU. If you prefer AMD your only option is to go with the 5700XT. If you use your PC for work or any other sort of CPU intensive application I'd upgrade my cpu, and preferably save up for a 3700x in your scenario.
GPU upgrade if only gaming
CPU upgrade if doing a combination of PC tasks
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