iOS 6 probably won't go down in history as a revolutionary update, but fortunately it's anti-tamper measures don't seem to have changed much either. The iPhone Dev-Team has already managed to get its redsn0w tethered jailbreak working, at least for the A4-powered iPhone 4, 3GS and 4th-gen iPod touch, and you'll find full instructions as well as a healthy list of caveats at the source link below. As to how long it'll take to get some Cydia action on the iPhone 5 and other fresher devices and without the hassle of tethering, place your bets here.