It takes the IOS SHSH 4.2b3 to jailbreak untethered to iOS 4.2GM

Saurik is saving IOS SHSH 4.2b3 to make a jailbreak in iOS 4.2GM untethered

What does this mean? Do we have to have the SHSH of the beta 3?

No, but i s likely to need the SHSH IOS 4.1 to be able to make a jailbreak iOS untethered in 4.2, because as you know the Limera1n exploit (which is currently using all known jailbreaks) is tethered, although it has been untethered make a jailbreak using another exploit of Comex. We know that Comex has new exploits in the manga, but just in case we recommend you save the IOS SHSH 4.1 By TinyUmbrella.

Note: no need to upgrade to 4.1 to save your SHSH, you can save it from previous versions as well.