The future design paradigm has been pretty much been exposed in a lot of the newer applications Apple debuted this/last year so I'd expect several more refinements before we get a major flush. Generally it works in a path like this: Apple introduces new applications which have custom/private UI elements, the following year they open them up to developers and expand on the prototyping from the previous year by introducing those trends to the major first party applications.
It was something started after iOS 7 and seems to be working well for them, so not major shift is needed, yet. Johnny Ive's redesign was pretty intense, but it forced a radically more aggressive development strategy for keeping the UI (and other components) fresh.
I personally love the current, upcoming design — it just took a long while to get there through many many steps.