Ink and paper is the way to go. Futureproof and non of that battery suddenly dying on you. It was used by geniuses like Leonardo Da Vinci and Albert Einstein, so I guess it must be good enough. No refreshes, just buy more ink and paper. You can use all the money you saved on stamps.
Have you even SEEN how thin they can make a sheet of paper? It makes the rMB look like a chunky old laptop from the early 2000s. It's amazing what technology can do these days.
I'd love to see an updated MacBook with a 720p camera, an extra Type-C port, and the ability to drive a 4K display at 60hz. If Apple did this, it would be the perfect consumer laptop. We're seeing a repeat of the MacBook Air where the first generation tests the waters and the succeeding generations get better and better.
I'm still hoping this isn't a replacement for the Air but more a companion device in the vein of an iPad that just happens to run OS X, though. Some people need a bit more power than Core M can currently provide without going up to rMBP territory. Still, down the road this could be the logical successor in future generations of the product if Intel can make the Core M series even better.