Sometimes we have the "itch" to upgrade.
You now have a well balanced system that seems to serve you well.
If you have some upgrade funds, perhaps there are some other upgrades that might serve you better.
If you do not use a ssd for windows, that would be very high on my list.
Perhaps you would get a better gaming experience with a higher resolution wide screen monitor.
If you think a processor upgrade would be good, run this simpleminded test:
Run YOUR games, but lower your resolution and eye candy.
If your FPS increases, it indicates that your cpu is strong enough to drive a better graphics configuration.
If your FPS stays the same, you are likely more cpu limited.
You are now on a very good 4th gen processor.
In the Intel world, the 9th gen processors are the latest.
You would get a very good boost in as little as a i5-9600K.
Not only would you get more cores, but you can look to a clock rate in the 5.0 range.
If one looks at task manager while gaming, you will see activity on all threads.
That does not mean that the game can make EFFECTIVE use of many threads, it is just windows spreading out the activity across many threads.
Remember that game developers want the largest possible market for their games.
If they develop a game that requires 8 threads to run, they will not sell many.
A high thread count processor is most effective with multiplayer games with a large number of participants.
Strategy games, sims and MMO tend to depend on the performance of the single master task.
What to do now???
That is up to you, and your wallet.
If budget is not a big problem, I say go and scratch that "itch"