This is the interpretation that Cook most likely meant. It refers to Jobs' comments years ago that tablets like the iPad are the future of computing. Laptops and Desktops as we use them today are "trucks" according to those comments. You still need them, but you aren't going to sell them to everyone when sedans will do.
The thing is, us debating on how useful the iPad is or how well it can replace a laptop is a bit like a bunch of ranchers saying how they could never use a 2-door convertible as their main work car. We are the part of the market most likely to be needing trucks, and having them around.
That said, I do agree that iOS has gaps that will prevent it from replacing laptops for many workflows. Some of it is hardware (the iPad Pro addresses a couple of them, while ignoring others). Some of it is software (extensions help make it a bit easier to access files between apps, but a shared file store would still be a huge boon). And some of it is apps that aren't being fleshed out enough on the tablet (which the Pro might spur some action on, it might not). So there is a bit of chicken/egg, but I don't disagree that tablets running something akin to iOS or Windows' "Modern" interface are the future. But it will be years before workflows for us truck drivers get anywhere near what's needed.
Agreed on basically all points, except that while "years" is clearly (to me) correct, it might turn out to be low single digits. It can't be as hard as Apple and Microsoft make it seem. The iPad Pro and the Surface Pro 3 are closing in on the same point. The question is whether either, or both, will get to the magic point, and when. Again, it really can't be as hard as they make it seem...