iOS 10 pretty much confirmed
The prototype owner managed to run Geekbench on the phone and racked up some decent scores - higher than the current iPhone 6s. We'd be surprised if it didn't, honestly. The big jump, from 4,427 (GSMArena's iPhone 6s test) to 5,210 (the prototype) for the multi-core test means that the new phones will most likely be running the new A10 chip.
What is slightly suspect is that the Geekbench test doesn't show the iPhone in the typical numbering system that the app uses. Geekbench usually names phones not by their commercial model names but, like in the case of the iPhone SE (which is called the iPhone8,4) goes by the numbering of the phone in the iPhone lineup. Still, it could be due to it being a new phone and thus not coded into Geekbench's current code.
This new phone might confirm that whatever changes are in the new iPhone are incremental at best. There likely won't be a capacitive Home button, retaining the current line's physical button but the iPad Pro's True Tone display might make it to this new iPhone, though screen sizes and resolutions won't change.
And the camera? Rumour is the iPhone 6 SE Plus will mimic LG G5's strategy to use different focal lengths for its dual cameras instead of Huawei's MO which is to use one sensor for black and white, with the other sensor shooting full colour.
The tipster also said that the old iPhone 6s will no longer be available in gold and rose gold, with only the silver and grey being available. You want gold or rose gold? You'll just have to buy an iPhone 6 SE then.