I I think it's going to be many years (5 mininum) before 8 cores are actually mainstream and used in games.
we've all heard the arguments before, like consoles using 8 cores for years now, and it hasn't made a difference.
pc devs target their audience, the average pc gamer has an i3 or i5 at best, which is what devs will program for.
even look at games on both systems, take big titles such as fallout 4. on console it runs on 8 slow add jaguar cores at 2ghz, and it's essentially perfectly multithreaded.
now on pc, you could take a 4ghz piledriver and it runs like crap because it's not multithreaded, because it runs better on a i3.
many many games that are indeed multithreaded on consoles are still single threaded when developed on pc.
even with ryzen, if you go off of amds 2% marketshare then you're saying roughly by the end of this year 3% or 4% of gamers by the end of this year will have more than 4 cores, so it's still going to be a minority of their target audience.
realistically if Intel pushes 6 cores and amd 8, 6 core cpus will be recommended maybe by 5 years time.