。
Something like that probably won't happen.
Literal
That-kind-of thing [topic-は] happen-not [conjecture-でしょう].
~でしょう is the polite conjectural ending, used for predictions or suppositions: 'probably,' 'I think,' 'wouldn't you say.' Distinct from だろう (the casual equivalent). そんなこと ('that kind of thing') is the standard demonstrative-noun phrase for referring abstractly to something just mentioned or implied.