I've been patiently waiting for a mobile device that can replace the notebook for almost a decade. Currently I'm settling for an ultra thin and light notebook, which is nice, but it's still a lot to carry around. And who wants to juggle data between a home/work PC, a notebook and their phone?
Now with things like the HDMI out port on the Droid X and Motorola's plan to release a 2ghz smartphone by the end of 2010, it's becoming a reality.
At 2ghz, running a lightweight mobile OS, there aren't any vital business or development apps you won't be able to run (minus high end media editing of course).
Add in the ability to port the display to any convenient monitor or HD TV and there's no longer a reason to carry a notebook around.
For rare Luddite locations that don't have HDMI compatible TV's you'd need bring along a flat panel screen of your own. No doubt companies will be manufacturing them specifically for use with HDMI compatible smartphones by next year at the latest. Alternatively you could bring a miniature projector instead.
For those occasions when the (impressive) state of speech to text technology isn't good enough there are bluetooth keyboards.
And this is just 2010. In the next year or two who knows how far the rapidly growing smartphone market will have pushed mobile technology.