Harry Kane's continuous stay at Tottenham isn't because he doesn't want to leave the North London club but because the club do not want to get rid of their most priced asset.
Last two summer transfer window ago, Manchester City were very serious in trying to bring him to the Etihad but was resisted by Tottenham who tried stalling the deal from going through by giving the the citizens conditions that was too difficult to be met. Kane should know that if there's anytime he can leave Tottenham, it's surely now.
It wouldn't be wrong either if Harry Kane had to last one more season at Tottenham, because he will definitely have a bigger chance to leave for another team after next season is over. But in my opinion this is a very different matter than now because the price factor will definitely be very different for him after next season, moreover he will also be one more year old so that other teams will start to make considerations that are more different than now.