There is a ton of misinformation about this bug out there. CDPR should be more clear on what it does and what it affects.
Pure supposition but, based on what I've read, I don't think it's as all encompassing as most fear. Most people hit are smack in the middle of Novigrad and even those who get it still frequently get XP for side missions, contracts, etc. I'm thinking it may either fix itself in game through forward progression or just apply to a narrow range of missions at a certain point in the game.
Since CDPR in their own statement said it shouldn't actually have a huge impact on forward progress I think it may resolve itself to some degree or another through normal play even without the patch.
Yes it effects Xbox one Version. The press reporting on this issue is awful. Most are saying it's from a patch despite the fact that all platforms are on different patch cycles. If it's patch related then it's from the Day One patch, not any released since then.