As I told you earlier that jailbreak iOS 5 is possible, now MuscleNerd of iPhone dev-team confirms that jailbreak iOS 5 has successfully ported to iPod touch 4G but it still tethered boot so far which means that you should connect to your computer on every reboot. Thanks dev-team.
For who don't know, Apple has announced iOS 5 yesterday in the WWDC 2011, if you want to know what's new on iOS 5 - Click Here, also you have to see the official iOS5 video. You have to know that iOS 5 is still available in beta version which only for developers, but don't worry you can download iOS 5 from direct links From Here.
Update: Redsn0w 0.9.8b1 jailbreak released. You can follow our step by step guide to jailbreak iOS 5 beta 1 - Click Here.