In the field I am in, it is common for us to issue a stop ship order to the warehouse for a new product that has not reached the customer. Then have the warehouse upgrade the firmware (and occasionally hardware, ouch) to fix a problem found late in the program cycle, or add a new feature.

This talk of the rev A, if it is a chip change, is highly unlikely. But firmware, I wouldn't be surprised.

I also wouldn't be surprised if they are holding back for a big release 'blast' just after the iPhone hits the street. Most of us have made our decision, but the unwashed masses are easily swayed by the glitter in the press.