A big part of it is going to be whether major cloud providers adopt these.
E.g. see http://www.anandtech.com/bench/product/1826?vs=1729 (6900k vs. 7700k) - there are quite a few relevant workloads where the 8 core loses significantly to the 4-core. Even stuff where you'd think more cores are really natural (such as POV-ray), the perf advantage of the 8-core over the 4-core is less than 50% (!). For an example where fewer faster cores obviously win, consider web-browsers: the 4-core is 36% faster in google octane v2.
Servers that have lots of independant tasks, on the other hand, will love this cheap many-cores. And coincidentally, servers often don't use AVX all that much anyhow.
If you pick a comparison where the clock speed isn't so far apart, things look different: http://www.anandtech.com/bench/product/1832?vs=1729
Of course, fewer cores usually means a higher available clock speed. Just pointing out it's not just "code isn't parallel enough" that drives the disparity.
To be specific: you can't get the equivalent of a 7700k with eight cores - the 6900k is (AFAIK) the next best thing, and by the looks of it, ryzen for all it's revolutionary improvements wrt bulldozer, is not all that different from a 6900k. AMD's own numbers place it at an identical single core perf.
If you're lucky enough to primarily be bottlenecked on parallel stuff: go nuts, of course!
In any case, I don't want to suggest I'm not happy with AMD finally being a real competitor, I'm just trying to temper expectations of intel-beating world domination. Most users aren't so lucky. Many people use laptops, and slow websites are more of a problem than slow handbrake sessions. For me, it's visual studio and various build/run cycles. Sure, some tools use more cores with the right settings, but it typically scales really disappointingly after around 2 or so. That overclocked 5820K would probably lose to a stock 7700k in my workload, and that's just annoying.