I have heard some say that 8 cores will be required for future games.
I think that is FUD perpetuated by AMD.
Game developers want the largest possible market for their games.
No game developer will willingly undertake the extra cost to make their game multi core enabled and also require many cores to run.
They would not sell many games.
Most games today only use 2-3 cores; rarely over 4.
Here is a set of older tests on the effect of many cores on FPS:
http://www.dsogaming.com/editorial/report-despite-claims-most-pc-games-are-still-unable-to-take-advantage-of-more-than-4-cpu-cores/
The conclusion is that PC games are unable to take advantage of more than 4 cores.
There are a few exceptions, FSX is supposed one. FSX uses threads to load textures, but I do not see that much core usage when I run FSX
It is more important that the cores be fast.
Another exception is multiplayer with many participants.
AMD hates that because their cores are somewhat less efficient than intel's. Perhaps 10% slower per clock.
That is also a motivation for DX12 , a technology that improves the efficiency of graphics drivers.
DX12 is most important for slow chips, but is irrelevant for $200 class intel cpu's.
Just because you see activity on windows task manager across all cores, do not assume your job is using all those threads.
What you are seeing is windows spreading the activity across all available threads.
Then there is "Amdahl's law" which limits how many threads can be useful, depending on the speed of the master thread.
https://en.wikipedia.org/wiki/Amdahl%27s_law
In the $200-$300 price bracket, You can safely buy most any cpu and it will do a good job with most graphics cards.
It is when you get to the top end cards like the GTX1080ti where individual core speed really counts.
I do not see that improving much in the future. Possibly with10nm canon lake or the amd response.
I do see much faster graphics cards on the horizon so stronger individual cores may well be what is needed.
For now, those with I7-4790K processors do not usually have a great need to replace their processors.
FX-8350 users do have a reason because of slow cores, not because of the number of threads.