The Dev-Team has announced via Twitter that they plan on releasing an untethered iOS 4.2.1 jailbreak that uses the 4.1 SHSH blobs (versus the dev-only 4.2b3 blobs that previous versions used). The updated redsn0w will first be released on Windows, followed by a Mac version. Please keep in mind that the jailbreaking process on Windows will be very slow, since it uses the iDevice’s filesystem (instead of RAM) while shifting the required jailbreak files around. Post-pwn, the device will function at a normal pace.
Since Apple still serves the 4.1 IPSW (not blobs!), we’ll do a Windows redsn0w release for untethered 4.2.1 via Monte-4.1@iFrank0 the Mac Monte-4.1 will follow the Win version (because there’s already Mac Monte-4.2b3 for devs)
Redsn0w’s recent switch to Monte-4.1 will allow all users to jailbreak their devices legally, since Apple still publicly serves the 4.1 IPSW.