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.
I agree with your opinion, besides being able to damage the device, it will also make the price of bitcoin decreases, of course considering that VGA Minea has also emerged with high BTC production capability, but with this low price, it is very influential on the current price of bitcoin, and I think if bitcoin can be mined easily just by using a smartphone, of course it will make the price of bitcoin even cheaper