iPhone hacker MuscluNerd tweeted some recent news regarding iPhone iOS 4.2.1 ^[1] unlock.

Current i4 unlock goal includes til 04.10.01 ^[2] (4.3b3). Very weird situation...vuln cmds are there, trying to invoke them!

ironically, the i4 unlock search has yielded 05.14 & 05.15 unlock 3G/3GS vectors... but i4 is 1st priority

Not much, but we see that the work is in progress. They have found necessary vulnerabilities and their target is even higher - iOS 4.3 ^[3] (baseband ^[4] 04.10.01). As a background effect they also might be able to unlock 05.14 and 05.15 basebands, so there might be a reason right now not to update baseband to version 06.15.

However this is not a promise and there are no due dates. So be patient, we know it is hard. All we know for sure is that iPhone iOS 4.2 ^[5]/4.3 unlock will not be released before iOS 4.3 release.