just (you) wait (and see)!
You will see that what I have told you or predicted will turn out to be true eventually. I know you're going to get that job, just you wait! Just wait and see, I bet Susan has completely forgiven you by now. You're going to regret the day you ever crossed me, just you wait and see!
(just) you ˈwaitused to emphasize a threat, warning or promise: Just you wait till your father gets home! ♢ I’ll be famous one day, just you wait!
See also: wait