With the 12-inch Macbook and 13" Macbook Air already clogging up the portfolio, I can see them dropping the MBP 13 and keeping just a single large MBP 15 model for the professional market.
iOS is nowhere near good enough for Apple to consider scaling back their x86 line too much further. Hardware wise the iPad Pro is really nice, but it doesn't even have mouse support! Android has had that since 2011 at least, but it doesn't have the same ecosystem of good quality work apps.
iOS doesn't have mouse support because Apple doesn't want it to, not because it's "not good enough".
I keep wondering when Apple is going to simply drop their traditional laptop and desktop business in favor of things like this. It's not a great leap of imagination to think of a desktop version of an iPad ala a Chromeboxesque approach.