Laptop PCs of the future
As is currently the case, most users will gravitate toward laptop computers that most closely approximate the desktop experience. That experience will be all about hands touching a massive next-generation UI where more screen real estate will be more important than a physical keyboard. That's why laptops will likely retain the clamshell design, but the bottom half will be all screen, just like the top half.
Many laptops will be able to function in multiple modes, opened flat for maximum screen size (the two screens working as one), clamshell with a virtual keyboard on the bottom, or the top twisted around like some of today's convertible tablets.
Both desktops and laptops will go the way of the iPod Touch -- everything disappears into the screen, which you navigate with your fingers.
The future direction of technology is always hard (and perilous) to predict. However, I think all these major hardware changes are nearly certain. And I don't see all this coming together in isolation, either, but as the result of an inexorable chain of causality.
If you accept the inevitability of the next-generation interface -- the UI with advanced versions of iPhone's multitouch, gestures, physics, 3-D and diminished role of symbolic representation (icons) -- then all the rest follows. Screens will grow. Big screens you touch will have to be pivoted at an angle because constant vertical or horizontal use will be awkward and uncomfortable. Mice will vanish because you'll touch on-screen objects directly. The screen will provide an incentive to get rid of keyboard.
And as people get used to this paradigm for their desktop-equivalent computers, laptops with similar designs will follow. The easiest way to maximize both screen size and portability will be with a two-screen clamshell configuration.
Of course, there are many hurdles yet to overcome. The OS vendors will have to put a lot of research into making products affordable. The entire industry will need to get behind next-gen systems with applications, utilities, hardware and peripherals.
But that's the direction we're going. And iPhone got there first.