As Gingerbread has been announced, and ready for public release tomorrow with the Nexus S launch, the internet is shifting to Google's next operating system, Honeycomb. The OS will be highly focused on tablet use, and we now know that it won't even require any physical keys on the devices in which it's installed on.
The Home, Menu, and Back buttons have been built right into the UI. Andy Rubin explains that the need for this change will be that the end user will always have quick and easy access to these UI commands at the bottom left, regardless of how the device is held.
Of course, not having any physical buttons is not a requirement. We can definitely seeing manufacturers keeping physical buttons for various reasons, but if they'd like to create a clean faced Android slate, the UI will now support them.