There are reports that point to a mini Pro iPad coming, and I definitely don't think the mini 4 is the end of the line for the form factor.
Especially if the 10.5" pro is to the mini what the 12.9" pro is to the 9.7" iPad Pro (i.e. a resolution and poi that makes split screen apps exactly 2x an iPad mini screen) then there is every reason to have the iPad mini Pro around as well.
After owning all sizes and models of iPad I have always returned to the mini form factor. I just love using it more and thus, despite the arguments otherwise, end up using it for more things, both productive and consumptive, than I have with any other iPad.
For me personally, and I think for a lot of people, a 7.9" Pro would be an instabuy. That said, the A8 (and A8X for that matter) have sown themselves to be one of the generations of SoC with real longevity and staying power. Besides the occasional safari tab reload when using the browser heavily, I haven't noticed any real slow downs, and I use a lot of diverse stuff on this thing.
Anyway, I do think a 7.9" Pro will happen alongside the next round of iPP updates. Be interesting to see how they do it though. I think they will leave the 9.7" the way it is, introduce its clone in the 7.9" screen size and then give the new 10.5" and 12.9" the A10X.
You know what, the more I think about it the more I think there's a good chance of a Pro 7.9". And I think the mini 4 being placed above the 'iPad' in the lineup is kind of positioning it in that position.
The rumours kept pointing to a 10.5" and an iPad mini with Pro features. I feel like all of this could very well point to a refreshed iPad Pro lineup with 3 sizes.
Even when you look at the current line up:
$799 iPad Pro 12.9" (last updated fall 2015)
$599 iPad Pro 9.7" (last updated spring 2016)
$399 iPad mini 4 (last updated fall 2015)
$329 iPad
I kept trying to figure out why they would place the mini 4 as a premium compared to the iPad when they've always used size to differentiate the lineup.
We could very well see the Pros all get updated together this fall:
$799 iPad Pro 12.9"
$599 iPad Pro 10.5"
$399 iPad Pro 7.9" (or some new slightly increased screen size that fits in the same body?)
$299 iPad 9.7"
$199 iPad 7.9" (being hopeful)