Tablets are here to stay, thanks to Apple perfecting the designs that a lot of companies had been producing a long time ago. For most people most of the time, they are sufficient, especially for casual home use where they will typically be used for reading email and Facebook.
Are they the future of computing, where we will all use a tablet as our only or primary computer? Emphatically not. Definitely not with current technology, for a couple of reasons.
First, a tablet is not big enough to hold many people's personal photo collections, let alone home movies and purchased entertainment. Either we need to store all of that online (with much bigger online storage quotas and internet plans than we have today, especially for mobile data) or we need an external hard drive.
Second, especially for iPads, they're not even designed to be used independently of a computer. You need to connect it to a host machine just to sync with iTunes and install apps, or at least you used to. If that's still the case, then you can't use an iPad on its own until you have a desktop computer to connect it to.
Third, a tablet is a terrible interface to do traditional office work on. The screen is far too small, and typing more than one sentence on a touch screen is a recipe for frustration. For traditional office work, we either need to radically redefine it and discover a new equivalent of touch typing for touch screens, or we need a dock with external screens, keyboard and mouse that will look suspiciously like a current office computer.
So tablets might be here to stay, but they're not on the verge of taking over from our desktops completely. While the iPhone forced mobile phone companies to start offering data quotas on ordinary plans to their customers, the iPad has not forced ISPs to offer anything over their ordinary, everyday plans. There's no power behind the platform and there's no drive from (most) businesses to get these machines working for them. It's not a dead end, but to start a new revolution, something else has to come with it.
Mokalus of Borg
PS - There's something missing from this puzzle, and I don't know what.
PPS - I imagine nobody does, or else they'd be doing it already.