I don't think the current gen CPUs are bottle-necking the top video cards, unless you're talking about the niche market where people play competitive settings and low all graphics settings. Most games when comparing high-end videocards run 1440p/4k resolution where the difference between a 9900K or Ryzen 1600 is barely noticeable.
There is games that will benefit from overclocked CPU, and there is a games for that doesn't really matter FPS at all.
But I think (and this is just my opinion) that next gen GPU will need more CPU power than current gen.
I understand your point and I can agree but, see. There is competitive games, and humm there is huge industry that sell for this market so much things and not only CPU/GPU... and Ryzen 1600 is not good choice for this.
This video is interesting and in the end they said that CPU matter but not GPU.
So yes if AMD want to not lose current selling speed, they need to release Zen 3.