Apple showed the included sheet on yesterday's WWDC with information on iOS 6. It says "IPv6 Support for Wi-Fi and LTE" in the right lower corner (right below the blue logo).
Let's analyze that:
- IPv6 support for Wifi is nothing new: an iPod Touch 4 with iOS 5 connected to Wifi will already handle IPv6 correctly (if IPv6 is offered by the LAN).
- IPv6 support for LTE is great ... as long as your iOS device supports LTE. I guess currently that is only the new iPad / iPad 3. A far as I know the iPhone 4 does not support LTE. I guess iOS 6 does not support any IPv6 tunnels, so your mobile operator also needs to offer IPv6. That's what T-Mobile in the US does (based on NAT64).
- Apparantly IPv6 support for 3G / UMTS / HSPA / HSDPA / EDGE / GPRS is not available. Pity.