The default clocks on the RTX 2080 Ti might not deliver the performance we deserved, but at least the overclocking potential is there. Professional overclocker KINGPIN managed to push the GPU clock to 2.41 GHz and GDDR6 VRAM frequencies to 8.63 GHz, breaking all the records in 3DMark and effectively ending the Titan V supremacy.
https://www.notebookcheck.net/Nvidia-RTX-2080-Ti-overclocked-to-2-4-GHz-on-LN2-ends-Titan-V-hegemony-in-3DMark.333384.0.html
The top end cards are going to show very little performance increase over the 1080ti at 1080p. These cards are fast enough that games are cpu bottlenecked at 1080p.