you'll, he'll, etc. 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.

ˈyou’ll, ˈhe’ll, etc. be lucky

(also ˈyou, ˈhe, etc. should be so lucky) (spoken) what you expect or hope for is unlikely to happen: You were hoping I’d come and collect you from the airport after midnight? You’ll be lucky! Try a taxi! ‘Come and see us if you are ever in Australia.’ ‘I should be so lucky.’
See also: lucky
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