From Googles IPv6 Implementors Conference 2010: T-Mobile’s presentation of IPv6 in their mobile network; specifically, they said very clearly that IPv6-only handsets is in the product pipeline; dual-stack will be too expensive for some 3GPP-specific reasons, so they’ll just NAT64 everything that’s not ready by then. In short: Make your content available over IPv6, or we will do the translation for you (and you may not like the results).