I skipped the 20 series as the performance uplift for the cost didn't make it a sensible purchase. I game at 4k and have done for many years. I may consider a 3080ti depending of perf uplift and of course associated cost.
Single GPU's are approaching to be able to deliver 4k with decent framerates and so what happens when decent FPS at 4k is reached? I guess you could stive for 240hz 4k but 4k 120hz will be enough resolution wise for most as the dream goal for graphics or associated ultrawide resolutions.
Before folk start calling that cards cant do 4k at sensible framerates, @ 4k you don't turn all game settings up to maximum. In fact many processing options are for lower resolutions to look better. So many game graphics options you actually turn off @4k, releasing processing power to increase framerates. Gfx card reviews to compare apples to apples leave everything on max and is not a fair representation of framerates when gaming at 4k.
Depending on relevant performance of the new gen it could be a card that will last me a good while for my resolution and my main games I regularly play. INsurgency Sandstorm, Squad and Post Scriptum.
Cant see folk with 2080ti's getting enough of a perf uplift with the 3000 cards and their associated price, depends what a 2nd hand 2080ti commands.