Four Island

It's time, folks! If you're jailbroken, backup your SHSH blobs! If you're not jailbroken, but want to be, backup your SHSH blobs! Don't know what they are or why you should do it? Well, to make a long story short, since the new bootrom version of the iPhone 3GS, iOS updates have been very controlled. Apple has set it up so that, if they are not currently offering SHSH blobs on their website for the pair of your iDevice and a specific iOS version, you are unable to load that version onto your iDevice (this obviously doesn't apply if the software is already installed). So, ever since then, jailbreakers have had a way of getting around this by backing up the SHSH blobs for their iDevice and iOS version so that if they ever need to downgrade to a specific version of iOS, they can. Note: you can only downgrade if you already have the SHSH blobs for that iOS version, and you can only backup your SHSH blobs while Apple still offers them. So, yeah. If you don't know how to backup your SHSH blobs, perform a Google search on a program called "TinyUmbrella".

Anyway, why am I saying this? Two reasons: first, it's November now, so, if we can believe Steve Jobs, iOS 4.2 should be coming out this month. If you upgrade to iOS 4.2 and are unhappy with your inability to jailbreak, if you have your iOS 4.1 SHSH blobs, you can always just downgrade. Second, there has been some exciting jailbreak news even before iOS 4.2 is out:

Anyone with blobs for 4.1 or earlier should be able to get an untethered 4.2 jailbreak; this is not done but is being actively worked on.

comex

It seems that this may work by pwning an iOS 4.1 IPSW and somehow using that with iOS 4.2; I don't quite know. :P Note, it may not be out very soon because:

However, a 4.2 jailbreak might be delayed because Cydia doesn't work on 4.2 yet. Not sure how close @chpwn is to finishing his fixes.

comex

Regardless, we can expect an untethered jailbreak for iOS 4.2 and until then, I'll be staying on iOS 4.1.

Finally, I think we can expect iOS 4.2 pretty soon because, not only is the iOS 4.2 GM release already out for developers, Apple has responded to the current problem with iOS 4.1 and daylight savings time. They have posted a support document to their website saying that you will need to set your alarms to repeat "Never" until November 7th. Whether the date specified is the release date of iOS 4.2 or it's just specified because that's when daylight savings time starts is unknown.