There no significant bottleneck in that setup, and if you overclocked it, there will be none or a negligible one. Now if you want to upgrade you cpu anyways you need to tell how much you're willing to spend, mainstream wise for the recommended high ends, 9700k
Also, thats not how bottleneck works, its not that simple as my CPU is running 100% my GPU 60%, therefore i have this monster bottleneck completely hogging my system.
But take not my word for it, there's some people using this extremely shady bottleneck calculator website:
https://thebottlenecker.com/calculator
just check it out and compare the 4770k with a GTX1080 wich is more or less the same performance as the 2070