Re: Wait, What?
You've hit the nail on the head. The lack of traction with mobile NFC payments has pretty much nothing to do with who makes the mobile device or its OS.
The big issue here is payment processor support. When you want to make an electronic payment, the payment processor needs to know how to handle the payment. This isn't a problem when you're just adding NFC payment support for an existing payment network. But for things like Google Wallet, that's a completely separate payment network that the provider needs to integrate with. These integrations aren't trivial matters, so the payment provider needs to know that it's going to make back its investment. However, until there are enough payment providers (and therefore enough retailers) using the network, nobody will bother using that payment method.
In other words, there's a bit of a catch-22. You need payment network support before people can pay using a new method, but payment provider support probably won't come until enough people are using the new payment method. This, more than anything else, is why Google Wallet hasn't really caught on.
The only way that Apple are going to make any headway here is if they manage to partner with an established, major payment network. We're talking the likes of Visa, Mastercard, Amex, etc - networks that most payment providers are already working with. If a retailer had the right equipment to be able to take NFC-based payments, they should (in theory) be able to instantly take iPhone NFC payments.
If Apple are going down this path, the question will be who they partner with. I have a lot of doubt around Visa and Mastercard, as they're more likely to want to build their own solution that ties in closer with their existing payWave and PayPass offerings. My guesses would be American Express or Diner's Club, as they're fairly widely accepted, and could use the Apple partnership to help expand their reach.