It was initially expected that the untethered iOS 4.2.1 jailbreak might be released somewhere around the Christmas Eve. But if this latest tweet by Comex is anything to go by, we may not see an untethered jailbreak for iOS 4.2.1 by this Christmas.
I think I’m going to miss my Christmas deadline…
It is to be noted however that the iPhone Dev-Team already has a backup plan ready, but that will require iOS 4.2b3 SHSH blobs for untethered jailbreak. Comex is said to have a more efficient userland-based untethered jailbreak method for iOS 4.2.1. This untethered solution will almost certainly be applicable to all current iOS 4.2.1 devices, including the new A4-based ones which includes iPhone 4, iPad, Apple TV 2G and iPod touch 4G.
<google 검색을 통한 본문 인용>
 
12월 25일 크리스마스날 ios 4.2.1 완탈을 공개하겠던 COMEX 팀이 공개를 연기한다는 글을 12월 23일(한국 오늘) 트위터에 공개했습니다. 
 
크리스마스 날짜에 맞추지 못하게 되었다고 하더군요.  아직 신기종인 아이폰4, 아이팟터치 4세대, 애플 TV 등의 탈옥에서 문제가 있답니다. 
 
조금만 더 기다려주셔야 될 것 같습니다. 진짜 슬픈 소식이네요 ㅠㅠ