Apple just released iOS 4.2 Gold Master for iPad, iPhone, and iPod Touch. This basically is the pre-release version before the public one gets shipped. In other words, we should see the iOS 4.2 released to the public in just a few day.
I’m not sure yet if iOS 4.2 GM holds any surprise, but as always, make sure to stay away from it for the time being if you care a lot about your jailbreak/unlock.