http://www.techradar.com/news/the-iphone-8-might-have-a-new-way-of-launching-siri

Based on the most recent speculation about the upcoming iPhone 8 (or whatever Apple names it), it sounds like the Touch ID and Home button is going to be banished from the front of the device, possibly ending up around the back instead.

That would mean one less way of launching Siri - Apple's digital assistant can be invoked with a long press on the Home button in the current iPhones, which is handy if you don't want to shout out a "hey Siri!" voice command to launch it, for whatever reason.