Depending upon the game you play bottlenecks maybe a concern. Depends on how important texture quality VS resolution will be for you. Many people claim being able to boost resolution can be default clean up the picture in some cases.
As a rule of thumb for me, when the discussion of UHD gaming comes into play, I generally try to throw small budgets out the window. You want to play in the UHD realm and spend some money, you minus well spend a bit more money and ensure your getting a more proper experience. Otherwise it comes out a wash in many cases.
While GPUs are certainly most important fact, CPUS still do play a serious role. Keep in mind many games even with 1080TIs and RTX 2080s still only push in the low 60s in some instances with some resolutions using i9 9900k's
My advice is pick a target window in terms of overall resolution, graphics quality setting and pick a price range you are comfortable with. Then weigh out what PC parts you can add that can meet those demands. If I were you I would seriously consider upgrading to a 300-350 cpu along with the graphics card. Maybe even look at the new RX radeon cards or possibly keep an eye on RTX 2700's as their price falls.
Personally I just upgraded my setup, originally I was ONLY looking to upgrade my motherboard and CPU from an i5 to an i7. Fast forward two weeks with a few issues thanks to a bad PSU and Im at a pretty much whole new computer. And part of the decision came from what I wanted to do, and what information I got back from benchmarks. I determined for what I wanted my current setup wasn't enough. I needed more parts. So I bit bullet.
Not everyone can afford to and I always say stick with what your comfortable with. But understand that certain areas of pc building when falling into the enthusiast realm come at a higher cost. And unless your willing to take said cost it may not be worth it in the end.
And 4k Resolution is most definitely in the enthusiast realm.
::EDIT:: and not to push aside the RTX2060, the standard and super a great cards, and I picked a 2060 Super this week. So its definitely a good card in its own right.