The iPad will motivate other manufacturers to produce similar devices. They will mostly be generic, PC-compatible computers in (more or less) cool-designed cases (although none will match iPad in production quality).
Most techies will prefer those generic devices over iPads (apart from those in for a really hard challenge, who will try to make iPad run Linux or othe generic OS).
On the other hand, iPad will become nowhere near a success of iPod and iPhone.
