It's always been an evolution. What we're seeing now is a trend towards cellular everywhere, and device-agnostic services (same phone number on your Apple Watch as your iPhone). The next shift seems like it will be greater situational awareness in your devices -- your device can understand its surroundings (ARKit), and what you look like (Face ID).
So phones as a category may lose their uniqueness, in that other devices can fill the same roll, but I think we'll always see an evolution of a phone -- that is, a pocketable connected computing device.