What do you think will replace the smartphones?
Do you really believe that would be possible one day?
Something like AR contact lens (mojo.vision) :P
Eye projector controlled with your thoughts.
Depends on which quality of smart phone, for which set of users, for how long, etc.
Desktops replace smartphones for heavy processing computer work. Real interactions and meetups replace smartphones. Onsite education or training replaces smartphone.
People who are old might not do too well with smartphones and might use ipads or nothing.
So maybe be a bit specific in your question. Because this is very vague.
A microchip embedded under our skin. Extracts and records data from our brain.
Same as in black mirror?