Daken

Ok. Nobody says that Daken will appear in the final Wolverine flick. However, just like with some other X-Men characters, this is the last chance of seeing him interact with Wolverine. Furthermore, the premise has already been set. As we all know, 2013's The Wolverine took place in Japan. So who is to say that Logan didn't make a child while there?

As I implied, there are no chances for Daken to appear in the final Wolverine flick. But if he will, this would be great fan-service. Furthermore, it would also lay the ground for further appearances of the character. And, if X-23 will indeed take Wolverine's place in the X-Men roster, Daken would be a perfect villain for her.