Question Do I REALLY Need to Upgrade my CPU for Nvidia's New GPUS?

Sep 18, 2020
Hello, Tom's Hardware family!
I've been thinking to upgrade my GPU for a long time and I suppose, this is a great time to upgrade my veteran Gigabyte GTX 1080 with Nvidia's next line of GPU(Preferably with 3080).
Now, here is my worry: Do I have to Upgrade also my I5 8400K CPU to get all benefits from 3080? This is worrisome for me cause as a person who lives in Turkey, unfortunately, we're not doing well economically and upgrading with my 1080 with a great GPU is already costly to add to that CPU and MOtherboard expenses and it will be waay too much for my pocket.
Now, to be able to give you guys a clearer picture of my situation let me give you some of my computer using habits.
I use my desktop for mainly entertainment purposes(mostly for gaming).
My desktop is connected to my 4k Samsung HDR Q6FN Tv. I usually play single player games with a great story(Divinity 2, Witcher 3, Kingdom Come etc...) after work. Since I use my tv as a monitor I don't care about anything higher 60Hertz.
All I care about great graphics and decent frame rates. (Minimum 40).
In the light of these pieces of information do I REALLY must get a new CPU and Motherboard or My current system (with 16 GM DDR4 Ram and 850 Silversonic Power supply) is enough for new GPUS?