I can't remember a single product that Apple has released that had new, or hidden features, that weren't present in the pre release announcement
If I'm wrong I'll hold my hands up, but I think all this speculation is nonsense. We'll have to wait for revision 2 to see what Apple will, and can do, differently.
All you guys have extremely short memories.
Here's a relevant example to point to: YouTube. YouTube for the iPhone was not announced or even hinted at during the original iPhone keynote. It wasn't until some time later, but was still prior to the iPhone's launch that the announcement was made and the app shown. Speculation at the time was that YouTube was not ready at the time of the keynote since they'd yet to convert all their videos into an iPhone compatible format.
But regardless of the reason for the staggered announcement, it's clear that there's precedence for this to happen.
The 3.2 SDK is wrapped in Apple's usually tight NDA but devs are bursting at the seams with what's there, and we've heard/seen "evidence" of some of it: 6 apps in the dock, video chat calls, web file downloads, a rudimentary file system, network printing, etc. Will all of it be on the iPad when they ship? Only time will tell. My guess is some additional stuff will be, and some won't be.
But let's not say that it's impossible because it hasn't happened before. It has happened before.
For my part, I believe the next rev of the iPhone and OS4 will be announced in late March, right around the time the wifi iPads ship. The iPads will ship with 3.2, with 4 becoming available in late June coinciding with shipping on the next gen iPhone.
My $.02.