I have to be honest with myself.
I barely use the capabilities of my laptop. I use it to surf the web, check e-mail, and such... and that is about it.
And frankly, that is a waste of all that equipment, and money.
At work, I use my workstation desktop Mac... and it stays at work.
At home, I don't want to work. I barely even want to acknowledge that I have a job...
I love the easy functionality of my iPhone. As a phone it is ridiculously intuitive to use and manage. (and mine is just a 1st gen, running the latest software, and about 60 apps... most of which I barely use, but are kind of fun.)
But the iPhone is too small to be my evening forum posting and news reading entertainment.
The laptop is big, heavy-ish, and frequently is tethered by it's power cord, but it is a nice experience. But what does that experience cost...
And when I leave home on a trip... the cables, and cords, and stuff... all has to come along. and is not online until I find a wifi network.
an iPad, however... could replace my laptop. It won't replace everyone's laptop, though... some people use theirs much more in-depth than I happen to do.
It could show me the web content I want to see in the evenings. It would stay online for a passenger in the car, or a map, not to mention be a portable video player for them... it would go with a minimum of cabling, such as a dock cable and AC adapter. (which my iPhone also requires on a trip already)
With a non-portable central machine at my home, a desktop, or a home-theater integrated mac doing the heavier lifting, I could definitely see an easy touch-based interface being the "front end" of my at-home computer use.
Things it needs:
1: Camera dongle. A video/still camera, possibly with an LED light/flash, maybe even infra-red illuminator... Unplug when not needed. They could even make the camera head swivel 180 degrees, for objective use or video call/chat. Or it could be dual-headed.
2: GPS antenna. The case back is aluminum... not great for radio waves anyway... a GPS receiver dongle in plastic, with an integrated antenna would not need to be big... and all of the sudden... you have iPhone-like behavior. iPhone is probably the preferred size for portable GPS device behavior, anyway... and not everyone perhaps would want a GPS in their iPad, just for around-the-house use. Maybe if it has a 30-pin pass-thru, the GPS and camera dongles could co-operate and provide an augmented reality system.
3: An aftermarket stylus, or finger tip point, for more precise graphical use. draw-on tablet peripherals are going toward underlying display... this has similar appeal, and will be seen by people as a digital sketchbook. Brushes already shows that Apple is thinking along the same lines.
4: VNC, or Apple-official screen sharing app. This device is actually big enough to work as a temporary control device for a remote computer. VNC already exists as an iPhone app... so it is already largely in place. Apple could perhaps even do better, as a companion to their "Remote" iTunes control app.
5: most important:
Imagination.
There are all sorts of places to take this tech. It may not be as well featured as it could be, it may not be perfect. Hardly anything ever is... But that doesn't mean there is no potential worth exploring.
Frankly, I would love to get ahold of an iPad and the recently demo'd Parrott quad-copter that flies by app-control. If it was great on an iPhone... imagine it on an iPad. There's your camera, right there... a UAV!
Honestly... if it isn't for you... there is something else that is right for you, and it very well could be a laptop, or an iPhone, or an iPod, or some other company's product.
But as for failure... I don't think it will be, even if it isn't a brand new concept. iPhone/iPodTouch can only be introduced as a new concept once. Scaling it up can't possibly live up to that gestalt shift.
What might fail, is the iPod Touch... caught in limbo between the iPad, and the iPod Nano with a camera....
I could see the iPod Touch and Nano fusing into one multi-touch product... camera equipped, multi-touch screen, iPhone/iPad OS, but smaller than iPhone by a slight amount, OLED screen, longer battery life, and all the more portable... like the nano's shape already is.
Drop the classic. Leave the shuffle tiny and screen-less... and then you would have just the iPod, the hybridization of current Nano, and current iPT... with the tech updates expected... flash capacity, screen and camera resolution updates, and such. Maybe even dock-able with the iPad, connector to connector, to slave the camera to the iPad, or sync/share the data files.