The first benchmarks of the NVIDIA GeForce RTX 2080 and the RTX 2080 Ti are here and seem to reflect what we've been expecting so far. While the RTX 2080 Ti posts some impressive performance numbers and is easily the most powerful GPU in this generation, the RTX 2080 is on par with the GTX 1080 Ti in performance while still costing US$200 dearer. While these numbers reflect non-RTX performance, it will still be sometime before the worth of these cards can be estimated on actual RTX-enabled games.
https://www.notebookcheck.net/NVIDIA-GeForce-RTX-benchmarks-RTX-2080-is-a-tough-sell-but-RTX-2080-Ti-absolutely-annihilates-everything.333326.0.html
Just keep in mind that in 12 months time HDMI 2.1 (with 4x the bandwidth of 2.0b) and Pci-e 4.0 are going to be everywhere. Consider carefully whether you are going to "need" that high end and very expensive card that will be utterly outdated in 12 months.