I don't know how many years has Kane left of his contract, but everything above one means that Levy will ask for Lukaku + money at least.A Kane for Lukaku swap is the only thing that makes sense. He's not coming back here; the economic terms are impossible.
Kane wants to win titles now and not hope for Conte to make Tottenham winners in the next couple of years. He also saw how players that leave (Eriksen, Walker, Trippier), all win trophies, so he's had enough of waiting. City is his first choice, but i am also pretty sure Chelsea is higher on the list than Tottenham.Kane is in form again, I doubt he's leaving.