It won't happen.
Smartphone for bitcoin mining? you are just destroying your phone.
Smartphone as digital wallet, you can simply download an app / wallet and that's how you make it as your wallet.
You can't write off the possibility of mining on a smart phone so simply. A few years ago people would call you "mad" if you told them there would be smart phones which could direct you to wherever you wanted to go. It may not come too quickly but it is possible.