Convergence.
We have already witnessed the convergence of PC and Laptop where the laptop can completely replace the PC.
We are now witnessing the convergence of Laptop, Tablet and Smartphone into a product that can replace PC, Laptop, Tablet, and Smartphone.
This is the natural progression of both battery and CPU efficiency.
I think we will see a divergence into two products: a phone/entertainment product that can fit in your pocket, and a larger-screened product that fits in your briefcase that you can read text and documents from without eyestrain, and which allows for some sort of full-size keyboard.
My attitude is that if it's too big to fit in my pocket, it might as well be big enough to have a 19"+ screen.