To play Devil's Advocate - don't you think the makers or HD-DVD thought the same thing? Beta? And countless other formats/devices?
I personally know lots of people that bought palm pilots back in their heyday because they were cool and they thought they'd use them only to not and after the had their fun with them - a few months later they were on the shelf.
Not saying the iPad will not be used. I'm just saying - time will tell. But statements like "it's just not possible" well - let's just say - ANYTHING is possible.
Not in this case.
The only way ipad could fail is if something out there were better. Even with the cascade of smartphones out there trying to take it down, the iPhone is selling like hotcakes. There's literally nothing in the ipad's category right now.