We can't say that yet. Harry Kane is a good palter and even as a 31-year-old player he had good performance in Bayern Munich and any team he played for them. I think Harry Kane can even have the chance to play in older age while being in the good form just like what Ronaldo is doing while is old.
But still, Harry Kane can't be a long-term investment for Bayern Munich.
I think Bayern can find his use still for 3-4 more years in my opinion. He is a top striker and Bayern have invested a lot in order to get him. Naturally they will use him for a long term and they certainly have bought enough time with this also for finding a young striker filled in with good potential. I think in 2-3 years Bayern will start looking for next striker.
By keeping Harry Kane for the next 3 to 4 year, it will not be a problems for Bayern Munich, because if you look at Harry Kane potential, it is almost the same as Lionel Messi and Ronaldo, but Harry Kane has not received as many award like these two player, but I am sure that now Harry Kane is already there the right club in Bayern Munich is certain that Harry Kane will win the champions league title this season and will win the individual golden boot title that many people are talking about, Harry Kane just needs to maintain his performance and maintain his stamina so he can performed his best for Bayern Munich.
Bayern Munich still has enough time to replace striker Harry Kane in the future but for now Bayern Munich will continue to keep him and has no intention of selling to any club.