Even though Comex said he wasn’t sure he was going to be able to meet his Christmas deadline for an untethered jailbreak, it does seem we’ll get a nice gift from the Dev Team after all. According to the Team’s blog, an updated version of RedSn0w that implements a “backup plan” will be released and will deliver an untethered jailbreak for iOS 4.2.1.

Things seem to be rushed a bit as the Dev Team is looking for beta testers to run this RedSn0w untethered jailbreak and make sure every bug is taken care of before the public release…

Feel like helping? Here is what you need to know:

(If you have an iPhone 3G, or an old-bootrom ipt2g or iPhone 3GS, you already have an untethered jailbreak!  Just use the latest public redsn0w.)

To keep things manageable, this will be a Mac-only test program.  We also request that any volunteers *NOT* need the ultrasn0w unlock (in case things go very wrong).

Right now, the “backup plan” requires that you have the 4.2b3 IPSW on your Mac, and that Cydia has your 4.2b3 SHSH hashes.  Please don’t pirate that 4.2b3 IPSW!  (We’re also working on a way that this technique might apply to all those with 4.1 IPSWs, but that’s not the first goal right now.)

If you fit all the above qualifications, please follow @redsn0w_testers on twitter for announcements, and use the comments section here for feedback.

The good news obviously is that we’ll get an untethered jailbreak this Christmas. The not-so-good news is that this jailbreak is just a “backup plan” that might be rushed out of the door to meet the Christmas deadline. However, I do trust MuscleNerd and the Dev Team to give us something that has thoroughly been tested.

This RedSn0w update will ship sometimes this weekend. It can be as early as tonight or as late as Sunday night.

What are you going to do? Will you try this untethered jailbreak right away, or will you wait a couple days to make sure all the kinks have been worked out?