I think Ciri, despite only appearing in The Witcher 3, is too close to Geralt but I wouldn't mind seeing another game in the universe. Since The Witcher 3 headed towards semi-open world, perhaps something in the vein of Skyrim where you get to create your own character (or perhaps Dragon Age Inquisition with simple voice sets) would be interesting to see. Of course I expect that would require a lot of work and an even larger landscape but it would be interesting regardless.