Jiraiya beating Itachi is a certainty, since Itachi himself admitted so. It might be a draw if they both die, but it will definitely end with Itachi dying.

Sasori will eat Itachi alive, just because he doesnt have real eyes, and one prick from him means death. I honestly believe that Sasori is one of the strongest and deadliest in Naruto. It just so happens that the ones to fight him were the worst possible enemies for his style (excluding Tsunade, who is his imminent death)