Camera modules are getting small, cheap and good enough that there is little reason not to include one. If it's there and you don't need it, fine - don't use it. If it's not there and you DO need it, you've just lost an opportunity.
Cameras are not just about taking fine/family photos, they're about taking impromptu snapshots with whatever imager is available, and now moreso about digitizing documents, OCR, augmented reality, barcodes, product lookup - all leveraging the iPad's capability if only it has a camera to capture the image.
One competing tablet already has 3 cameras, including a pair for 3D. Heck, stick on four front-facing cameras and it could create a virtual full-3D videophone (watches the viewer's eyes, interpolating and rendering the correct 3D viewing angle). There: I'm up to 8 cameras (front & back) for way-cool effects (near-true 3D, not just stereoscopy) and not even trying.