Most don't you are right, but some are toying with the idea of proxying UPnP requests to "NAT Centres" on the carriers backbone; there are a significant percent

Most don't you are right, but some are toying with the idea of proxying UPnP requests to "NAT Centres" on the carriers backbone; there are a significant percentage of users who will refuse to put down their controllers and will walk to another provider. The other way this may be solved is to form a technology solution with the console makers to have a drop in solution at the API level; obviously this will disadvantage smaller developers who can't pay to play (not that this will bother the carriers overly). I suspect most likely in the US there will be a nuisance fee add on to your internet connection in order to play "P2P" games (x.ref current Net Nutrality battles in the courts)