What indications makes you think the Pros will be updated next year?
Because I don't see that happening.
I see 2019 as more likely time to see the next update. Force touch, OLED, and other goodies...
Correct on the first part, I think 18 months is the minimum cycle for now. Probably 18 months plus delays.
No Force Touch. That much is certain. Apple sees force touch as something you use on a device that you're holding with the same or other hand (phone) or wrist (Watch), so you can provide a "force" with one part of your body to contrast the force you put on the screen. Alternatively, with a laptop, you're pressing into the desk, or whatever surface the laptop is resting against. But the iPad is designed for a use mode where it's sitting on a surface with a Smart Cover or keyboard. Use force touch against the upright display and you slide it right away from you. That's called samsung design.
Who is "we"?
I'm beginning to believe that the 2nd gen 12.9 Pro is the last model of that form factor. I would not be surprised to see an 11.7" Pro with the 10.5 bezel sizes.
It may be that the 12.9 display size has run its course, but if it gets replaced, it will be replaced by something larger that fits in (almost) the same shell as the current 12.9 -- just like it happened for the 9.7->10.5 transition. I doubt Apple will give up on the large (12"+) iPad format, because its claims that the iPad is a laptop replacement rest 100% on that model, not on the smaller, eBook-reading tablet. (And don't get me wrong, I own and love both!)
I don’t think a bezel reduction is particularly likely to happen.
Current left/right bezel ratios relative to display width:
7.9": 5.9 %
9.7": 7.3 %
10.5": 4.4 %
12.9": 6.1 %
Current top/bottom bezel ratios relative to display height:
7.9": 13.2 %
9.7": 10.9 %
10.5": 8.7 %
12.9": 8.3 %
So the left/right bezel isn’t that bad on the 12.9" (it’s roughly the same as for the iPad mini 4), and the 12.9" actually has the smallest top/bottom bezel ratio of the current iPad line, including the 10.5".
This is a good point. My feeling though is that they will trim it if they can, simply because that is the design direction. The ratios you provide make sense, but obviously on the bigger iPad those bezel are still bigger, arguably unnecessarily so from an engineering viewpoint.