The 8 core version is not there to compete with the i7-7700K, no matter how much we'd love it to be in the same price bracket. I reckon the 6 core version will be in that range, and considering B350/X370 motherboards are likely to be cheaper than Z270 ones it should compete extremely well. Even if it can't quite reach the IPC or clock speeds, those extra cores and lower price should see the 4 and 6 core versions sell in bucket loads, especially as games more and more demand extra cores (be it virtual or real). It's not out of the question that the i5 range becomes redundant due to 4 core Ryzens, it all depends on the price and clock speed potential.
This is pretty much what I've been thinking all along.
AMD 4c/8t vs Intel i5
AMD 6c/12t vs Intel 4c/8t i7
AMD 8c/16t vs higher end multi-core intels (i7 or however they are branded)
That makes more sens to me than the dream of 8c/16t AMD's at 4c/8t Intel prices. I just don't see that as even a remote possibility. Assuming they are close on performance to similar c/t intels.