Instead, on November 12, Apple delivered a second Golden Master of iOS 4.2 to iPhone, iPad, and iPod Touch developers. The second GM was delivered, most suspect, due to a bug found in the iPad's Wi-Fi performance.
After the second Golden Master was seeded, reports of the final version's appearance ranged from November 16 all the way through November 30.
Earlier today, 9to5mac suggested that the final version of iOS 4.2 would be pushed out to end users at 1PM EST. That didn't happen. Instead, Apple kicked a third Golden Master of iOS out the door to devs.
The latest version, iOS 4.2.1, is believed to address a reported VoIP bug affecting the system. The VoIP bug was called "severe" by some, though specifics weren't reported.
This third Golden Master is being provided to developers only, who are expected to test it for problems. Developers will likely need at least several days to discover and report back to Apple any potential problems.
The iPad experienced Wi-Fi problems when it was first released, prompting Apple to provide a minor update to its software. There's no word if the previous bug is related to the old one, or if the new VoIP bug is specific to the iPhone, iPad, iPod Touch, or all of the above.
As per usual, Apple is remaining mum. Apple often does not provide specific dates and times for iPhone and iPad software updates.