Let's talk about technical upgrades.
XY and ORAS brought us up into full 3D, and it seems to me that every Gen has brought us at least something new to the graphical table. This would suggest that Sun and Moon will bring us something too. Will the Pokémon models be particularly changed, with more polygons, wider colour ranges, or complex battle animations? Or do you think we're likely to see essentially imports of what we have in Gen 6 as Game Freak focus on other things?
Perhaps they'll add more opportunities for the 3DS to utilise true 3D in the overworld. Whilst I've never played XY and can't comment on them much, I've found places like Petalburg Forest and Sky Pillar to be among the best places in ORAS for looks, and the 3D no doubt helped there. I don't expect them to make the entire overworld 3D, but more areas with it would be appreciated.
With the release of the New 3DS last year, it seems likely that they'll make some opportunities for owners to use the C-Stick and ZR/ZL buttons in Sun and Moon. I reckon it would have to be shortcuts to features that you can already access from the menu, though, so as not to disadvantage 3DS owners.
And perhaps they'll optimise Gen 7 enough that lag in 3D-enabled battles and triple battles is finally gone, or at the very least significantly reduced. Maybe it's too ambitious a task, but we'll see in due time.
Any thoughts on what I've said here? Or feel free to add something I've missed.