Tim Coook has weighed in about the future of tablets, at least those that are not Apple's. He feels that tablet/laptop hybrids have no place in the marketplace.
While he may have something of a point, given the checkered history of tablet computing, he may have a point. I suspect that there is more to this. Obviously, simply adding a keyboard to an iPad makes it a fairly decent laptop replacement (with caveats). The most inexpensive laptop that Apple produces is on average nearly twice as expensive as an iPad, so perhaps Cook is looking out for another product line, though the iOS products are Apple's biggest sellers.
It has also been suggested that Apple may be planning such a device. To be honest, I doubt that. The iPad is such a well designed gadget that simply adding a keyboard suffices for that "hybrid".
I think that what we're really seeing here is marketing, plain and simple. Apple would rather have you purchase their masterfully crafted devices than those less refined from their competitors.
Still, I also suspect that such devices are coming.