MG Seigler compares the weights of some leading e-readers, phones, and tablets to visualize where the iPad Mini, or Air, may stack up:
As you can see, this new iPad would be closest to the Kindle with a keyboard in weight. It would weigh noticeably less than a Nexus 7. It would weigh less than half of what all of the current iPads weigh. And it would weigh just a third of what a Surface running Windows Pro will weigh.
Yesterday I held a Nexus 7 (thanks Jeff) for the first time. It is incredibly light. Remember, I'm used to lugging around an iPad 2. The iPad 2 is downright heavy when compared to the Nexus 7. Jeff was walking around with the Nexus 7 in his back pants pocket! I'll admit it, I was jealous.
If the iPad Mini, or Air, or whatever Cook & Co. call it, weighs in anywhere near these estimates, and costs anywhere near $200, and has the features of the existing iPads, it is going to be a smash hit. Even bigger than the iPad is now.
(This isn't to say I'll be getting one. I do not know if I need the ~8" form-factor. I use my iPad every single day and while it would be nice to have a smaller, easier to handle, iPad I can't see springing for one out the gate. I'd probably weight until I retire my current iPad 2 and pick up the second-generation iPad Air (I'll stick with this, though I doubt Apple will) at that time.)