This is an environment very similar to what you encounter today if you venture inside an Apple Store where most POS tasks are executed on iPhones. This is an environment where the company (personnel) comes to you, instead of the other way around.
This step by AT&T is also aligned with a trend within POS where retail outlets get rid of specialty hardware POS solutions and instead adopt iOS solutions which are much cheaper, easier to use and can provide added functionality. You can already see the effects of this when you go to your local gelato store, but it is clear that major retailers now are quickly moving in this direction too.
The future of POS will be a future without specialty HW and centered around iOS applications as a replacement. It will provide with increased flexibility, added functionality and lowered costs. It is entirely possible that the current partnerships between payment industry and tech industry on NFC will struggle because of the same reasons.
My personal view is also that NFC will become overrun by this development. The functionality of NFC can be added to the app-layer instead for faster adoption, added functionality and it will be easier to use.