I disagree. I see the mobile computing market falling into three categories now:
1) Smartphones. These are taking the place of the netbooks of old that were tiny (i.e. 9-10"). Plenty capable of doing e-mail, texting, IM, etc., and somehow, folks are browsing the web with them too.
2) Newer netbooks. Anywhere from 9-12" with an emphasis on low power consumption and better battery life. You do e-mail, web, and all of that jazz as with smartphones but with considerable amentities that make traditional computing possible (e.g. better keyboard, larger screen, numerous ports for expandability).
3) Desktop replacement laptops. Anything larger and more powerful than the netbook described in #2. They come with even larger screens, full sized keyboard with numeric keypads, discrete graphics chips, and beefier internals like large hard drives, optical drives, multiple cores, and Library of Congress sized RAM. While "portable," the downside is that you're chained to an electrical outlet, because these bad boys devour electricity. Some have coal-fired chipsets in them (just kidding).
I'd argue that #2 will be the largest source of growth in PCs (including smartphones) in the next few years. Unless you sleep in a different city every night or need to get your pixel shading game on, these new netbooks will fill your needs toward both ends of the scale very nicely. It's a big, wide bell curve that favors the new netbooks.