As per iOS developer Guilherme Rambo, he had leaked some of the details about the iPhone 8 previously from the Apple Homepod firmware which leaked the some of the cameras feature of the iPhone 8.
I did find a gesture to invoke Siri by holding the lock button.— Guilherme Rambo (@_inside) September 2, 2017
As per earlier leaks, this time Apple upcoming iPhone 8 is no longer having a Home button instead will have new Gesture features and an all new Software bar from where you can launch apps and even there is no longer support for Touch ID which is replaced by the 3D Facial recognition system.As there is no longer Home button which was previously used to launch the Siri by long pressing the home button, now Apple is implementing the new way to launch Siri by pressing the Power key.Apple will also keep the Hey, Siri functionality.
Apple is also planning to launch its very first Apple 4K HDR TV with new iPhones. There are also rumors of all new Apple watch LTE edition to be launched on Sept 12.