After Steve destroyed physical keyboards at Macworld 2007, I think that the chances of him placing a keyboard on the iPhone are... unlikely, to say the least. More like impossible. The power of the iphone lies in its ability to change the UI, and one element of the UI is the keyboard. So I don't think that the iPhone will ever have a physical keyboard. The OLED keyboard patented by Apple may be more likely, as it could change the look of the keys/keypad. But then it would simply be another touchscreen.
A better idea than a physical keyboard would be to put a landscape keyboard in every app, except without the "previous, next, done" buttons/banner at the top. That way, business users could get the larger keypad in apps other than Safari, such as notes or mail, and it still has all the benefits of the touchscreen.
What I really want to see in iPhone 2.0 would be a landscape mode of every standard app, and the homescreen (the icons could simply turn sideways, and the multiple screens could swipe sideways, or take the "wheel" look, where you scroll up and down.
Some really nice "possibilities" would be the dual-sided transparent multi-touch surface, the full-body touchscreen, or a "haptic" AND multi-touch screen.
Either way, the iPhone is still the most advanced cell phone in the world. Its design is impeccable, and the form factor is excellent (although thinner would be cool). I can't wait till June (new MacBooks) and the iPhone 2.0 upgrade!