Google Wallet doesn't have anything to do with technology. It's just an app, that has limited popularity around the world and has a lot of competitors.

You can set NFC always to on and just click a button to confirm payment. Or not to click anything for trusted clients. There could be many ways to use this technology. And metro systems can offer own NFC programs.

I'd guess it will be one or two more years until we see more use of the NFC technology. Theres still alot of hasle with the standards that are not really there, yet. Everybody involved into this want to keep as much of this technology for himself in order to have the biggest piece of the cake. I mean, I can totaly understand that from a business point of view, but in the end it's one of the reasons why NFC doesn't really take off. The big players need to realize that they won't make the big money if this technology never takes of f and thus at some point a compromise will be found which will lead to more standardized approaches to nfc.