Plenty of people here will help you overclock that Ryzen chip, they only really go to around 3.9ghz, 4ghz if you get really lucky. But you should be able to hit 3.9ghz with decent cooling on a 1700x. What you are getting is future proofing, while we are only on the start of more games using more cores, it is happening, take BF1 for example, it will happily chug through cores if you have them.
The higher the resolution you go the more you rely on your GPU, obviously your CPU needs to feed it but your becoming more GPU bound as you go up in res.
I wont lie, the 7700k is probably a better chip for single threaded stuff currently, but the fact that MMORPGs generally run ok on most setups means the 7700k is kinda overkill really, the Ryzen chips are equally as good, go seek some benchmark vids on Youtube, this guys running WoW on a 1700X with everything on max bar a couple of settings that notoriously cripple perf, he has a 1080 also and getting 70+ FPS https://www.youtube.com/watch?v=Jq8nPT_TlsQ
So yeah Ryzen will keep you happy in MMO's no problems, my brother has a Ryzen 1700 and plays PoE pretty much exclusively, and he raves about how good that chip is, although he came from a 2500k lol, but its still an i5.
Haha, I've been watching some benchmarks and that and If I can make this old hunk of junk stretch I think it may be worth waiting for the I7 8700K as it's performance seems blistering in both aspects, while I do love the idea of the Ryzen waiting that bit of extra time if I can, I could put some more cash away and push a better mobo/ram combo.