My prediction: Always on video/ audio recording in wearable form factor (probably glasses).

This seems "creepy" now, but people thought that about Google "reading" all your email too. The benefits of an ever present and aware assistant are just to great to ignore.

Apple's angle is that they are well liked and trusted (much more so than Facebook which people already think is eavesdropping on them to show ads) and will do all processing on device.