I agree that form factors are v. important and in many cases are the "decider" for a lot of customers.
Much work is now going on to deliver a very small compute/capability kernel which can be inserted into different form factor "shells" as required. Think of it as a fully featured PC (not a pocket pc) and a multi-band mobile phone and a media player all on a device about the size of a PCMCIA card (but its def. NOT a pcmcia card!
This device is then inserted into whatever shell the user fancies - phone shaped (whatever that means - but it probably has good tactile digit keys for a starter!) Currently the device slides into a test phone behind the battery (its ablut the same size n shape!)
or - the device can be inserted into a shell with a bigger screen for gaming/reading/viewing. Even plugged into your 42" plasma when you get home.....New shells could be designed as and when required. And discarded when the HCI interface becomes dated...but the basic compute capability would still be valid. Shells available today contain powerful graphics sub-systems (or is it super-systems - lets settle on exosystems) and truly massive storage systems.
This means that the form factor is sorted...the content will be the differentiator of the future. Sound interesting?
I know that these will be "on the street" very very soon - be very afraid.....