David Wagner, the Huddersfield manager, is being linked with the Wolfsburg position. I wouldn't have been surprised if Mooy being sent there was partly due to Wagner managing the team and the style he plays. If Wagner does leave, then I think we should seriously consider recalling Mooy as we don't know who will be brought in and how that will affect his playing time/position. Similar situation to how Roberts at Celtic has had limited opportunities now that Rodgers has taken over.
Is Mooy a replacement for Gundogan? No, he is not that skilled. However he offers much more going forward than Fernando, and as he isn't crocked, so obviously offers more than Delph currently. We could do a lot worse than him to be honest, and we won't be paying overs to find a replacement in January. I think the last short term January signing who was actually a decent player was Pizarro, and I'm not sure how likely it is to find a player of similar ability, who'd be happy to be a stop gap this time round.
Or we could try and recall Nasri!