With the iPhone 8 allegedly jumping to 5.8 inches and going bezel-less, they should refresh iOS with interface elements placed closer to the bottom for easier thumb access.
Apple should embrace the Apple Watch as a notifications hub: allow third-party developers to use custom sounds alerts and/or haptic feedback patterns with notifications.
If the 5.8" iPhone Pro rumors are to be true, I can see Apple embracing multi-tasking in the form of dockable widgets. Not to be confused with Android's split-screen apps that are literally apps chopped in half, but the ability to dock widget-versions of apps.
In theory, iOS 10's iMessage Stickers should be as popular as Line/WeChat stickers in Asia. In practice, iOS 10's sticker interface is too clunky. I expect a "Favorite Stickers" section and other improvements to encourage better engagement among iMessage users.
I see Apple's new Clips app as a hint for native third-party camera filters for iOS. It will allow third-party developers to create Snapchat-like filters that can be seamlessly added to — and removed from — photos/video directly from the Camera Roll.
Building on my Dockable Widgets prediction that assumes a 5.8" iPhone Pro, I think Apple will finally include picture-in-picture video support for iPhone.
I'll be surprised if Apple markets the next iPhone as "The 10th Anniversary iPhone." Surely they will highlight how the iPhone changed the world in the past 10 years, but I think they've learned from their costly mistakes of past "anniversary" products.
I think it will simply be called: iPhone Pro.