1.15 is indeed the most current App Store version.
I would be pretty sure that even on iOS 10 that the App Store will show the latest updates (my iOS6 devices still do!), but only those that can be run on iOS10, which are probably less and less as Apple makes it harder and harder for devs to support lower versions.
FYI, MidiFire 2.0 is getting near. The lowest I am now able to target is iOS8 (and I have tried (without success) loads of tricks to retain iOS 6 and 7 compatibility). I was only able to target iOS8 as I use as much non-deprecable hand-written code as possible.
Thanks, Nic. It's good to hear that a MF update is on the way. Having done a lot of work in MF recently I have a few ideas which I'll put in the suggestion box. Thanks as always for your support. Dave.