From what I understand, the idea is that the first few batches will go to hackers so they (we) can get to work stress-testing and creating with these. After we're done, they'll sell the next batch to the education market hopefully with the new tools/accessories that the hacker community had come up with.
Can't create much when we can't see schematics and ascertain if the I/O ports carry what we need. And if there was a deficiency, they've publicly said they won't respin boards.
They do plan (and will have) IO extensions ala Arduino. I can't remember what they call the daughterboard they're releasing.
Mainly what they want is software and cases. It's meant to teach kids computer programming and software basics outside of the Windows and OSX "don't worry about it" mindset they're currently growing up in. Robotics and extraneous hardware design is outside of their current scope.
If you're thinking of the "gertboard" that was announced, that's a breakout board that is connected to the Rpi over a SPI line. So it's not turning GPIO lines off the processor into usable connections, it's just an I/O extender. You could be using that exact same board with an Arduino today and bit-bang your SPI commands.
