[doublepost=1477672915][/doublepost]when the iPad type of device will diminish as importance (see sales decline continuously) we may see a combo device iOS and macOS, independent to each other but with possibility of working together at some levels....we take off iPhone from this equation because we need its size in a pocket...but the iPhone will greatly benefit in future connections with the MacBook and iMac (macOS) because of the direction of the development between the macOS and iOS on the same machine: MacBook
This would be immense, expensive, but immense. The iPad Pro is 6.9mm 'thin' with a brilliant display and touch interface. Design a connection that would allow a Mac to drive the display and use the touch input and you'd really get the best of both worlds.
Alternatively have a native 'trackpad' mode for the iPad that would turn it into a context aware second screen/tablet input for MacOS with, if you're using an iPad Pro, full Apple Pencil support!
YOU got it!