Everyone keeps saying the iPad Pro will be updated - but what if it isn't? What if, rather than updating, Apple simply cuts the price?
Moving to that system - iPad Mini and Air 2 being cheapest, Pros coming at mid range and high end, Apple squeezes two years out of each design. Release at higher price, price cut a year in, update 9-12 months later. As the iPad's profits are a small fraction for Apple, it's not exactly a stretch to think that they'd take that approach.
I'd say, at best, we'll see new watch bands, a 32/128 option for the SE, and price drops on iPads. I don't expect a10x upgrades, boosted RAM in iPads, the 10.5" model that there's been zero evidence of.
It would also explain the new identifiers - four iPads for the four current models, re-released for 2017.