As there are a growing number of people foregoing a land line for owning just a cell phone, I expect we will start seeing people who do not bother owning a desktop or laptop PC, but just use their phones.
Unless you are doing serious processor stuff like editing videos, a cell phone could do a lot of what people want, only if it were not for the tiny keyboard.
Put your iPhone into a keyboard like this, and you can seriously generate e-mails, and write notes. You could even produce documents and store them on the cloud and later print them out at the library, work, school or Fedex Office.
Pictured is the Ion iType (via RegHardware)
If rumors are true and Apple announces its iSlate Tablet computer later this month, and it is priced about $1000, would you buy one if you already owned a high end phone and a laptop? It might be difficult to cost justify it if you already have a good laptop.
What if, there was a good keyboard for it, and a easel type stand that could hold it up like a laptop? Then you could justify the cost and use it as a tablet in the field, but as a laptop in the home or office.
Update : After posting this, I am watching Leo Laporte's live coverage of CES on Twit Live. He mentioned the Lenova new laptop coming later this year, where you can run Windows, then disconnect the screen and it acts as a tablet. That may be the best of both worlds.
Update #2 - 01-09-2010 : Engadget reports some unfortunate details : "Unfortunately, because of the closed nature of most of the iPhone platform, you can't just start typing in any iPhone app; you have to type in the iType app and then copy and paste to the app you want. It's surely an annoyance, but if you're sick of the soft keyboard and need some relief, it's your best option for now."
Lenova IdeaPad U1 Hybrid via Pocket Lint