I understand your thinking but I'm pretty sure you are way off in your conclusion. Apple releasing what will effectively be a new iPad line in the 10.5" screen will be marketed as a premium device with high end features and price to match. I would say it is much more likely to be like the 9.7 Pro but with the 12.9 screen resolution due to reduced bezel size i.e. true tone, quad speakers & smart connector with Pencil support but with a newer SOC and more RAM.
Time will tell though.
Could be. Certainly would be a high end device, but still LCD, not Amoled.
I just don't see them doing one year of the 9.7 Pro form factor (and upgraded screen, and 4 speakers), then moving to the 10.5, while still keeping the 12" as a Pro in the old "bezel" style, either.
Nor then keeping that "old" 9.7 Pro around as a Pro if there is something that is the same physical size but a bigger screen, nor rebadging it and calling it the Air 3.
3 Pros (Mini, 9.7, 12.9) 9.7 gets a bit of a price drop to be the cheapest of that size (or keeps price, but pencil now included), goes in tune with the marketing ads where the Pro will be the volume seller now. Not 100% sure there will be a Mini Pro.
1 Air (10.5) - less specs, but bigger wow factor.
1 Mini (Mini 4, whether there is a Mini Pro or not, or, the Mini 2 lives as the cheapest Ipad as the Mini 4 is dropped/upgraded to the Mini Pro)
Air 2 dropped, Mini 2 or 4 maybe dropped.
Or, yes, you're right...10.5 Pro, 12 Pro (but look totally different - this is where and why I don't think Apple markets two different looking devices as Pro - just not their symmetrical style). Mini, who knows, as above.
9.7 Pro is dropped, Air 3 is an upgraded Air 2 with a cheap price point
Mini is up in the air as scenario 1.