Square the circle
Blackberry is still caught between a rock and hard place. Their devices have smaller screens due to the space the keyboard takes up, and even Apple has thrown in the towel and given people larger screens.
They could try to get around this by making a slide out keyboard phone (e.g. the Torch). But in the past these have always been fat, and the keyboard has been rubbish compared to those on the standard candybar Blackberrys. Unless they had do some engineering alchemy and produce a slider that is under 9.5mm thick and has a decent keyboard I think they are toast in the long term too, as the market for candybar Blackberries just isn't large enough on its own.
They should have three devices - a candybar phone with keyboard, a unicorn slider, and a iPhone alike without a physical keyboard (but with that trackpad button that the new classic has for placing the caret when editing text).