I don't think 4k is likely to become the new normal for PC gaming. I think it'll be 1440p at 100+FPS. But that probably shouldn't change your approach.
Why not just wait? They're announcing the new cards today. Price drops will start happening soon and will obviously peak when new cards ship. The difference between a 2080 super and a 2080 ti is not necessarily huge in terms of FPS in current games, but it's significant in terms of futureproofing.
https://gpu.userbenchmark.com/Compar...-Ti/4050vs4027