I'm sure phone providers will find a way to configure their links so that they work the same as with IPv4 (i.e. no incoming connection allowed). This isn't even necessarily a bad thing - remember all these jailbroken iphones with the default root password running an sshd? While not providing perfect security by a long shot, denying all incoming connections to a client on the firewall can help mitigate some issues.
It also "fixes" a lot of potential "problems" like people running p2p software on their phones or using VoIP instead of the much higher priced voice calls by the phone proivder (yes. voip works today, but it could work ever so much better if these devices were accessible directly)
One of Australia's 3g networks had an alternate APN you could use that gave you direct access to the internet, and an externally facing IP address. I only discovered this last month and the network is being shut down this year. It's such a pity this isn't a standard feature.
Would be nice if they gave you an Internet facing IPv6 address by default, but default firewall rules that blocked incoming connections, and the ability to modify those rules for your connection only.
But I guess that would only be valuable if they also gave you a static IP. And static IPs for client devices like phones aren't exactly a good thing from a privacy perspective. Ideally you'd have both a dynamic and a static IP, and new outgoing connections would originate from the dynamic one.
I wouldn't want to run a Web server or SMTP server on Dynamic DNS. The delays introduced by DNS cache when your IP changes provide an opportunity for somebody else to intercept/replace your traffic. Although I admit that is pretty unlikely.
I get no ipv6 connectivity on my sgh989 (tmobile usa ver of galaxys2) when on 4g (turning off wifi). On wifi, I get ipv6 (local net has ipv6 connectivity).
Could it be regional... T-Mobile enabling ipv6 for some cities and not others? Or perhaps the current tmobile firmware (mine is 2.3.6, T989, UVKL1) for their sgh989 disables ipv6 for the gsm/utms portion of the radio.