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.
Bayern Munich will not spend large sums of money to bring in a 31 year old player if there is nothing special about the player. It is clear that Bayern Munich is investing in Harry Kane, his performance is still very good and in his first season in the Bundesliga his name was immediately displayed on the temporary top scorer list.
Kane is still very productive even though he is over 30, his physique is still very good. Bayern Munich can still rely on him for a few more years, if they find an ideal replacement who is younger, maybe Kane will be sold to an Arab club to reduce the huge costs they spent when they brought him in.