According to numerous sources, Apple will be releasing iTunes 10.1 on Wednesday, the 10th and iOS 4.2 on Friday, the 12th. Apparently, 4.2 was delayed due to a problem with displaying Japanese characters correctly, but this issue has since been fixed.
This update will have many improvements and fixes, including support for multitasking (and other 4.x features) on the iPad, wireless printing, AirPlay, and a fix for the lock-screen bug that allows anyone to bypass the phone’s passcode, as well as the DST bug that caused quite a few people to sleep in.
This version is also said to remedy the slowdown that is currently plaguing iPhone 3G users, but this has yet to be officially confirmed.
Also, remember to backup your SHSH blobs, since a jailbreak for 4.2 will probably be released soon.