Yes a 1080Ti is perfect for 3440x1440 60/100hz. I love my pg348Q.
But in most games your going to be struggling to get anything above that without reducing quite a few settings to get near the 144hz never mind 200hz.
This is true, although the noticeable benefits beyond 100Hz are diminishing, and as has already been mentioned, 200Hz is just a gimmick. Not that anyone is going to turn their nose up at Volta or whatever follows the 1080Ti, but this monitor is hardly going to prove 'useless' if you already have one. Of greater concern should be actual game support for HDR, which I suspect will be hit and miss for a while. Xbox Scorpio should actually help in that regard though, as no doubt that will push devs to cater for it.