If Dany was smart, she'll kill Jon and Tyrion before they get the chance to get to her, like on the way home, then go burn Winterfell to the ground with Sansa in it. The line has been crossed, their betrayal is inevitable.
What I think will happen is Tyrion gets executed, Jon talks to Dany alone to see if she's really as gone as she thinks she is, then does it himself within her embrace like she knows she deserves it. Unless Greyworm accepts Jon as the rightful heir, he dies, too, and everyone goes home.