If Jesus hadn't existed, it would matter! It would not be a revealed religion any more but a myth. However, will it ever be proven? Proving that Jesus didn't exist is much harded proving that he did exist. As you probably already know, his existence is not only based on biased biblical stories but also on some research from the Jewish historian Flavius Josephus...
I can argue that even if some strong evidence show that Jesus hadn't existed, the christian believers will just dismiss or even ignore these facts. Religion is about emotions, not about reason!