1
general::
Phrase(s): (Are you) leaving so soon? [and] You leaving so soon?
a polite inquiry made to a guest who has announced a departure. (Appropriate only for the first few guests to leave. It would seem sarcastic to say this to the last guest to leave or one who is leaving very late at night.) • Sue: We really must go. Sally: Leaving so soon? Sue: Fred has to catch a plane at five in the morning. • John (seeing Tom at the door): You leaving so soon? Tom: Yes, thanks for inviting me. I really have to go. John: Well, good night, then.
McGrawhill's American Idioms And Phrasal Verbs