I have a slightly different take -- I think that 'next thing' is AR (glasses, contacts, etc.), and I think Apple is as poised as anyone to take advantage of it.

The big revolutions in computing devices have been room full of equipment + punch cards -> desktop w/ big display -> laptop w/ small display -> phone with really small display.

I think the logical next move after isn't ever-bigger phones/phablets/tablets, it's contact lens / glasses device with A/R display.