Ciri is a Witcher, no doubt about it. She has all the training of a Witcher, was practically raised by a Witcher, and I'm 99.99% sure she goes through the trials before Witcher 4. It's impossible to know if 4 will top 3 but it 100% has the potential to. And also, I think most people who have an understanding of the lore/story of the novels and how it connects to the game had an understanding that if the narrative went on long enough Ciri would take over, I think plenty of people wanted her. And, in all honesty, what lore changes are you so worried about?