Sigh, not this again. We already had a monster thread about this with the last rumor post. The firmware adds more features than 4.1 (AirPlay, Printing, etc), it takes time to test those features, work out the bugs, etc, especially on the iPad which hasn't had 4.x yet. The new version (4.2) will come out for ALL devices in November, not just the iPad, which means they have to test it on ALL devices. It takes time, that is all. They have to also give time for app developers to update and test their own software. I would imagine the SDK will be out by the end of the month.
If Apple was releasing new hardware in November, we would see an announcement about it within the next 15-20 days. They would not just go "surprise!!" and suddenly have them on shelves without putting some effort to market the new product and also give a window for early reviewers/developers. It would also be really odd considering the iPad is not even available in some countries yet. They are more than likely ramping up the releases for those countries (like China) and trying to sell as many 1st gen iPads as they can before next year when they announce the 2nd gen.
It would also be supply-demand suicide for the upcoming holiday sales season. Why screw up the curve when they are just now getting control on it?