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

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