This fact cannot stressed enough! Every time people are warned about updates from Apple disabling Jailbreak / Unlock , some people still end up accidentally updating via iTunes. Why take a chance while you can get the new iPhone firmware goodness with a few days wait?
Launch iTunes, Click on Preferences – > Under General Tab Uncheck ‘Check for new software updates automatically‘. Wait for a confirmed jailbreak and unlock for the newly released firmware and then update.
One question in mind!! how about for people who havent bought an iphone 3gs yet? are future iphones will be jailbreakable?