Good question.
It depends on the player, really. Luka Modric was desperate to join Chelsea in 2011 but Levy refused to sell. Modric went on to have an outstanding season before joining Real Madrid the following summer.
Kane, likewise, is desperate to join City this summer. My guess is that, if denied that opportunity, he will also act professionally. He has too much personal ambition and pride to waste a season by sulking or refusing to play or train to his utmost.
On the flip side, I could ask whether you would sell arguably the best all round striker / creator in the world; a home grown player; a talisman; the England captain; for less than you believe him to be worth when he still has 3 years remaining on his contract? That will be Daniel Levy’s stance.