iPod, iPhone and iPad are great products. But the issue is that they come in different sizes. I agree that each has different screen dimensions that require a different physical product size. So for different screen size, we need to carry different physical size devices.
I think the next big product would be to remove this limitation of different screen-sizes and then device sizes.
I am still waiting for the device that will have variable screen size and smallest possible device size. When you are on move and want to make a call, the screen would be of iPhone size. When you are relaxing at home the screen would be of a 52 inch TV. When you are on your desk, typing emails, the screen would be of your desktop size. When you are making a presentation, the screen would be of size according to the room. But the device itself would have the smallest possible physical dimensions.
Our data is going to reside in cloud, we still carry and use different devices for same thing like- checking email, watching videos, browsing etc.
Pranav Mistry had come up with a demo of similar idea in 2009. But till date there is no real consumer product for this.
As Apple is obsessed with letter i and P in the names of its products, it looks like iProj to be a new product name for such a Product.