Joshua Hill, an iPhone developer of the Chronic Dev Team has recently publicly confirmed that an updated version of GreenPoison is going to be released. For now he is working on sandbox patches for this release.
GreenPois0n is actually based on Geohot’s Limera1n bootrom exploit which has already pwned all current iOS devices for life. This release of GreenPois0n though will most likely be a tethered jailbreak, much like what Redsn0w 0.9.6b6 can already achieve.
iPhone 3GS (new bootrom), iPhone 4, iPad, iPod touch 2G (MC Model), iPod touch 3G and the iPod touch 4G will support a semi-tethered or tethered Jailbreak, while Old devices like iPhone 3GS (old bootrom), iPhone 3G and iPod touch 2G (Non-MC Model) can be jailbroken–untethered using this version of GreenPoison.