Today, apple has released the 4.3.2 firmware for iPhone (AT&T GSM), iPad, and iPod touch, and 4.2.7 for iPhone (Verizon). The update includes security fixes. Since Jailbreak exploits security holes, there's every chance the update may patch something crucial to the current iOS 4.3.1/4.2.6 Jailbreaks. That means if you update, you may lose your Jailbreak.
We're hearing the Jailbreak for 4.2.1 still works, but not the untethered version. Either way we recommend being safe rather than sorry and holding off on any update until the Jailbreak developers provide further information. Same goes for unlockers -- stay away.
In the meantime, make sure you save your SHSH blobs with tinyumbrella (Cydia isn't enough).
We'll update everyone as soon as we know more, and be sure to check out our Jailbreak Forums to keep up with the latest!