I'll be seeing you
Also, see you. Goodbye, as in I have to go now; I'll be seeing you, or All right, see you. These colloquial formulas do not necessarily imply a future meeting. [Late 1800s]
The American Heritage® Idioms Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.