Anyone who has paid by smartphone at retail will recognize that it's not really ready for primetime. It's pretty surprising that retailers are using it at all considering how inefficient and time consuming it is compared to other payment methods.
Any solution that requires fidgeting with phone apps, internet connectivity, waiting for confirmations etc. is a non-starter for any mainstream retail environment. There's just no way it will be adopted until a workable alternative similar to existing payment methods comes along.
You probably never tried a smartphone wallet-to-wallet transaction. It's pretty straightforward, no fiddling involved (given connectivity, I always have problems with that

). No waiting for confirmations needed, that's a common misconception.
The sentence "there's just no way it will be adopted" is plain ignorant.
It already
is adopted by a growing number of merchants.
I am unsure wether merchants will sooner or later start using specialized hardware for it (I'd expect specialized POS-hardware for connectivity to legacy cash registers etc.), but rest assured, clients
will just use their smartphones.
The reason is simple, they already have that.
Easy to setup, easy to use, easy to build an infrastructure.
And it's safe and convenient
enough.
The idea of a specialized Bitcoin card, specialized hardware like the trezor etc. has been around for years. For some use cases, there's some merit to these ideas. Not for brick-and-mortar point of sales, though.