The next Apple special event will take place on Wednesday the 9th September 2015 at 6pm UK time. You can find details of the event here and for the first time, the stream will be available to Windows devices, as long as you are using Windows 10!
It's pretty certain the new iPhone 6S will be announced, rumours state it will have a new camera which will perhaps have new lenses and maybe record in 4K video resolution.
A successor to the 3rd generation Apple TV may also be announced. It is rumoured Apple is working on its own TV 'like' service but this has been delayed until next year. Perhaps the new Apple TV will be 4K compatible and might start to form the centre/hub of Apple's HomeKit compatible devices.
Other than that, who knows. Apple like to keep everything under tight wraps until they actually announce it, we don't have long to wait though!