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

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