I don't see a 6800xt getting 120fps at 3440x1440 given that the demo shown yesterday was running on an Xbox Series X, which is basically a 6700xt, and it was dipping under 30fps.
Now admittingly the demo did look like 4k type of sharpness, but still 4k 25-30fps doesn't translate to 120fps at 3440x1440.
Doing some back of the hand maths, 30fps with 8 million pixels (4k) translates to 50fps with 5 million pixels (your 3440x1440 QD-OLED). Now your 6800xt is better than a 6700xt by about 25% according to hardware unboxed and 50 X 1.25 = 62fps
So in conclusion your QD-OLED with a 6800xt will get about 60fps, with some drops under 60fps. Luckily though the game isn't launching soon and performance may improve by launch