we must do lunch sometime

We should really get together at some point in the future, ostensibly to have lunch. A clichéd, noncommittal expression often associated with upper-class people. A: "I'd love to sit down with you sometime and go over some ideas I have for the business." B: "Oh yes, of course. We must do lunch sometime—call my assistant to arrange a date." I really must run, darling, but we simply must do lunch sometime! I'd love to catch up with you soon.