you, he, etc. will be lucky

(one) will be lucky

That is very unlikely to happen or be the case. The phrase is used sarcastically or with a sense of resignation. And just who is going to pay me back for this thing now? I'll be lucky if I get 50 bucks for it at a pawn shop!
See also: lucky, will
Farlex Dictionary of Idioms.

you, he, etc. will be lucky (or should be so lucky)

used to say that someone's wishes or expectations are unlikely to be fulfilled.
See also: lucky, will
Farlex Partner Idioms Dictionary
See also:
  • (one) will be lucky
  • (one) would be lucky
  • (one) should be so lucky
  • barrel of fun
  • are we having fun yet
  • Are we having fun yet?
  • AWHFY
  • this ought to be good
  • this should be good
  • bright idea