Doh! It just struck me - everyone here is either saying Apple can't add a physical keyboard because SJ trashed phone keyboards etc or that a physical keyboard for the iPhone is a must.
BUT THERE IS ANOTHER WAY.
Supposing the sliding out keyboard turns out to be...another touch screen keyboard! Because it's touch screen it could be thin enough not to make the iPhone any much bigger, it would increase the screen real estate enormously by effectively producing two touch screens, and if it came out the side you could rotate it and have a landscape touchscreen keyboard and full iPhone screen page to write on. Sorted!
And it wouldn't compromise SJ's stance on physical key keyboards...
i actually really like this idea, sounds like something apple might actually do!