Klopp was seen in Dortmund training recently. It was really good to see him back there even though he wasn't there to coach. 
Klopp is very valuable for this team and the fans. He also knows that.
One day maybe he might be back to manage. However if Nuri Şahin is doing really good things there in that time then Klopp's team would be different. I don't think he would return to Liverpool after managing them for around 10 years.
But I would love to see him managing a German team again someday before his retirement. Because for now it doesn't seem like he has left his job for good.
Good news for Dortmund fans, but confusing with all this. I mean, if Dortmund really wanted Klopp back, when they heard the news that Klopp wanted to leave Liverpool, Dortmund should have made an offer to the coach. But looking at some of the news, it seems like this will be a strategy that we will not know and give a nice surprise when secretly having an agreement between Klopp and Dortmund. And for Nuri Şahin, I am actually not sure if he will really be able to make a change but we will see in the next few games whether he can maintain Dortmund consistency. Klopp is very valuable for this team and the fans. He also knows that.One day maybe he might be back to manage. However if Nuri Şahin is doing really good things there in that time then Klopp's team would be different. I don't think he would return to Liverpool after managing them for around 10 years.
But I would love to see him managing a German team again someday before his retirement. Because for now it doesn't seem like he has left his job for good.