This level of performance is only just starting to tackle 4K at 60FPS reasonably for most high end games I’d imagine, if comparable gaming PCs available today are any indication.
You shouldn't need anything high end except the GPU, for the rest of the components it would be like hitting 60fps in 1080p.
The 2080ti is the fastest gaming GPU on the market right now. Period. It does not matter what your budget is, you cannot buy a faster GPU that that. Even if you buy a $10,000 quadro, you won't more than 5% extra performance in a best case scenario over the 2080ti.
RTX 2080 Ti SLI (NVLink) Battlefield 4 [8K 60FPS]: https://www.youtube.com/watch?v=GBqjy7bCoBE
Call of Duty: Modern Warfare (2019) - 8k 60FPS [RTX ON] 2x RTX 2080 Ti Max Settings: https://www.youtube.com/watch?v=qMVWRrOmSCQ
It'll be much the same way that an Xbox One S renders games at 1080p, but supports 2160p60 output, with a 1:4 upscaled output. The upscaler is not a difficult piece of silicon.