、。
If he were to meet you, he'd surely be surprised.
Literal
By-chance he [subject-が] you [to-に] meet-[conditional-ば], he [topic-は] will-be-surprised [counterfactual-だろうに].
だろうに adds a counterfactual regret/wish nuance — 'would probably X (but it's not happening).' The に at the end of だろう tags on a sense of 'alas,' 'unfortunately,' 'even though.' It's a slightly literary/emotive construction.