There was some sort of casual "open microphone" banter between Trump and Kennedy that came out in the last couple of days from some affair and they seem very friendly. Something about how grateful Kennedy was to Trump's family for how well they are treating some family member of his in NYC and Trump telling him what a great kid he is, how everyone loves him. Sometimes relationships matter and Kennedy might feel comfortable letting Trump replace him, even if they don't see eye to eye on everything.
Trump just did replace Kennedy. Now we have to hope that Kennedy retires and Trump can replace Scalia.