The iOS 9 manifest file is out there and some people have been doing serious digging around in it. In fact, somebody has even found some tasty morsels on the iPhone 6S front-facing camera.
In the code there are suggestions of front facing 1080p recording and a front-facing flash as well.
The code also includes "Front60FPSVideo," "FrontSlomo" and "FrontPanorama" suggesting all these features are coming soon.
At the moment there's no front-facing flash on the iPhone 6 or iPhone 6 Plus and the front camera is only capable of 720p video recording at 30fps.
Panoramic photos on your front facing camera sounds a little complicated but slow-motion video is a great idea, and the rumour is it'll be 240fps as well.