Hmm, whilst I appreciate the abilities of the 12.9", that statement is incredibly subjective. It inevitably varies from person to person, but in my case using a large iPad instead of a small laptop offers less flexibility and less usability. Portability and ease of access for certain tasks, and obviously design/art related exercises it smokes a laptop, but otherwise it's all very much a "diet" laptop. Which is absolutely fine for lots of people, but also totally inadequate for many others.
I really like the iPad, but when I hear iPad evangelists trumpet the abilities of it as a complete laptop replacement, followed by the long list of workarounds they need to do to achieve this, I think....hmm, sounds like a pita and it's hardly efficient is it?
I'm not suggesting the 12.9" isn't a highly capable device, but it's incredibly limited for myriad purposes and the imminent demise of the laptop is exaggerated. A smart keyboard is a good accessory, but absolutely pales in comparison to a good keyboard and large trackpad for general usability. The iPP, large or small, is a pretty awful experience when using the smart keyboard on your lap. I've little doubt that large tablets will catch up over time in this regard, but so long as the interface is mimicking laptops and not introducing an entirely new control paradigm that betters traditional keyboard and trackpad, it's always going to be a compromise. No interest in a Surface Book personally, but that's where everything is probably headed, albeit in a much more streamlined form.