I think people who believe tablets are going to replace the PC are missing the point. One of the big concepts we're building at my work is the idea of devices that are designed around limited input scenarios.

In other words we believe there's room for two types of devices: Viewing devices with limited input (like tablets) and input devices (like PCs)

To give a personal example the most obvious usage case here is the e-book. If you could have every book you've ever owned at the touch of your finger that would be worth something even if you were limited to basic input on the device. Now combine e-books with all your movies and music and you start to see how there's room for devices with limited input.

(For the record we've been using ELO Touch Screens to test usage scenarios until the perfect tablet shows up)