Absolutely NOT!! Do not upgrade if u intend on keeping the jailbreak. There's an untethered jailbreak for 4.3 on it's way. Besides, I'd hold off till all your jailbreak Apps are also upgraded for 4.3 compatibility. This could take a couple of months till there is a stable untethered release and for all the jailbreak apps to update. So be patient; it's gonna take a while. Hold Off.