iOS 6.1.3 is only in beta right now, so the matter isn't that urgent, but it looks like when it does come out, it's going to eat your jailbreak for breakfast and keep you from fixing it. Seems that Apple has fixed one of the five crucial exploits evasi0n needs to survive. One of evasi0n's creators, David Wang, explained the bad news to Forbes:
"If one of the vulnerabilities doesn't work, evasi0n doesn't work. We could replace that part with a different vulnerability, but [Apple] will probably fix most if not all of the bugs we've used when 6.1.3 comes out."
So it's not the end of the jailbreaking line, but with each batch of patched exploits, the job is going to get that much harder. And So if you've got a jailbreaked device, don't don't don't install any updates without a little research. You should probably wait for word from the evad3rs themselves. [Forbes]