He wanted to meet this man called Otto. As this was the last time he would meet this guy (a second father to him) he thought they would both cry, embrace and just plain behave like a son who is separated from his father. But he knew that Otto would probably just shake his hand as if he was not that important to him. He was prepared for that reaction.
This is the best rephrasing I can muster.
"that would be that."
This means "that's it". In other words, we can assume they would never meet again.
Student or Learner