For anyone wondering why he hasn't been playing at all for Dortmund, I remember reading somewhere he has picked up an injury and has been out for over the past month. It makes sense, I couldn't understand why he wasn't even on the bench in many of the past games.
Regarding youth leaving, it will happen, Pep is doing a much better job this season than last (obviously it was his first year) and with the stability around the club I imagine next year we will see youth play more and more, excited to see Nmecha, Diaz and Foden more and more.
One thing people should realize is that there are more and more great youth players popping up everywhere (not just City) due to populations growth, but we have the same amount of clubs, every club will find it difficult to hold on to youth. City have to try to their best to give the cream of the crop chances here and there, but many have to leave to play and kick start their careers, there is no room for great prospects at City, you have to be a phenomenal prospect.