That idea is completely, laughably absurd.
Tech is unpredictable - technology doesn't follow a predictable path
No, the idea is sound and most probably correct. Companies that don't plan five years ahead are usually reactionary: they look to see what's happening in the market and look to take advantage.
Apple is fortunate enough to have considerable influence in technological trends, so yes, they will be planning and designing products that will not see the light of day for years. In many cases they will start to design products and wait for the technology to make them viable. The iPhone was on the deck years before it was released, or do you think that the thing was designed, engineered, programmed, approved, sold to the networks and then marketed in the space of a few months? If they weren't working on the iPhone while they were getting ready to release the first iPod then I'd be very surprised.