Beginning on July 21, we started seeing a small number of hits from devices running iOS 9.1. Visits picked up on July 22 and peaked in the dozens on July 28, before dying down as August approached. The majority of hits we received came from an iPad or iPad mini-sized device, while the rest came from a device the same size as the iPhone 6 Plus. It is not clear if the visits came from existing iOS devices or from new devices that are in testing, including the iPhone 6s Plus and the iPad mini 3.
Visits from iOS 9.1 devices have since tapered off, suggesting Apple's iOS team is once again working on getting iOS 9 ready for launch. It is not known why a two week period was spent on iOS 9.1, but it's possibly related to testing on the iPad Pro or iPad mini 4, both of which may already be in production or entering production soon.
We don't know what features will be introduced in iOS 9.1, but logic dictates it may be an update that's designed to launch alongside the larger-screened 12.9-inch "iPad Pro," which has been rumored to be coming in October or November. We did not, however, see visits from a device that corresponds to the rumored 2732 x 2048 display size of the iPad Pro.
For the past several years, Apple's iPads have debuted during the fall, launching in October or November at an event separate from the annual iPhone event. This year, there's been a rumor suggesting the next-generation iPads, namely the iPad mini 4, could debut in September alongside the iPhones, but it is not yet clear if this is Apple's plan.
BuzzFeed's John Paczkowski, who shared the event date for the 2015 iPhone 6 launch, believes new iPads are a possibility, but called the iPad Pro a "wildcard" for the event. Given how little we've heard about the device in recent weeks and the lack of part leaks, it seems unlikely the iPad Pro is ready for a September debut.
A standalone October or November launch date for the device seems more likely, and that launch could correspond to the iOS 9.1 update that is in the works. The iPad Pro may include several new features that will require a dedicated update, such as a pressure sensitive Force Touch display, a stylus, and a USB-C port that could support peripheral devices.