Apart from Nubel, I think Bayern Munich seems interested in the Argentinian goalkeeper in the World Cup - Emiliano Martinez to be their main goalkeeper this season. Neuer looks set to be out for quite a while due to injury. Nubel seems to have no more interest in returning to Bayern Munich, but anything can happen in the end. So it's true, Nubel may not want to be a substitute player who sits more on the bench throughout the season.
For sure Nübel dosnt want to be again on the bench when Manuel Neuer is back again and full of health.
Emiliano Martinez is also already 30 and maybe they try to get him for at least an contract of 3 or 4 years.
This would be pushing his Career , but i think that there also other Clubs now will be knocking on his door.
Anyway, I'm really not sure about Neuer when he recovers he will regain his main place at Bayern Munich, because the injury is severe enough that it will likely make it difficult for Neuer to regain his best form. So, whoever the goalkeeper will replace Neuer during Neuer's injury period, I'm sure the goalkeeper will still get his main place in the Bayern Munich squad.
At this moment, it is no longer because Neuer is a legendary player and team captain, but because considering his condition that it is no longer possible to play in every match, of course Neuer will likely be backed up more often in the future.
I only consider that Buffon was also at Juventus when his position began to be replaced, at that time Buffon as a team legend and team captain could accept the rotation done.
So, it doesn't mean that when Neuer returns he isn't needed because we also have to look at the fact that Neuer is old and has a serious injury, so of course it's difficult to continue playing, especially since the competition is very tough.