They could very well exist, there's just no way of knowing in what manner they exist. It would be another Mirror Universe situation where a lot of them could be living entirely different lives, or largely the same lives, just totally irrelevant to the story at hand.
Guinan. She would be the one prominent TNG-era character who should be mostly untouched in this timeline. As would Q, I suppose, but I'd rather they not go there, unless it's to finally out him as Trelane.