iOS 9.1 Update
And finally, it's worth noting that we've learned a little bit about what should be the iPhone 6s' first major iOS update.
Apple is reportedly working on an iOS 9.1 update behind the scenes. The update is reportedly going to arrive in October alongside a new 12-inch iPad Pro. If this holds up, it means that it will likely be released in October as well. (Same as iOS 8.1.)
iOS x.1 updates are typically more than minor bug fixers so we could see Apple add some new features for iPhone about a month after the iPhone 6s release.