I think people are putting 2 and 2 together. Sales are down, we are reaching saturation point with household tablets and consumers are keeping tablets for anywhere between 2-4 years before upgrading. It would be sensible for Apple to push the upgrade cycle to a longer time. Look at the Mini, we only saw a Mini 3 last year as it only added the TouchID sensor, as Apple obviously wanted TouchID in all their products as fast as they can. And we haven't seen and Air 3 this year. Yes it was to give the Pro some breathing space, and of course Apple won't make the mistake of putting out an Air 3 with virtually the same processor specs as the Pro at the same time.
I do expect the Air 3 in the Spring though, with a slightly paired down A9X, still with only 2Gb RAM and not the 4Gb that the Pro is getting. We will then have 3 separate iPad models with varying power. Then in Spring 2017, we should see a refresh of all 3 models housing an A9 (Mini 5), A10 (Air 4) and A10X (Pro 2).
This is just my opinion though.