To summarise what I know and have found out:
1. The old 30 pin connector does not have an RF connection (as pointed out by Technic). The snap in adapter provides inductive coupling from the iPhone antenna to the cars antenna. There is no direct connection.
2. The new 9 pin connector is a digital interface. The adapter has a chip that is used to verify the connection as legitimate. It may also do some protocol conversion, not sure about that.
3. The adapter does not support the so called iPod interface protocol (which was supported over the USB interface) so there will be no control of the play back system and cover displays etc. from iDrive. Presumably this is a protocol change so it is possible that BMW can update software to use the new interface.
4. The analogue component and composite video interface in the old 30 pin connector is no longer supported, so the video feed in the current BMW iDrive interface will no longer work. Presumably the new 9 pin connection supports a digital interface (probably some variant of HDMI) which will require more than a software change to iDrive. If a new adapter is designed it will need to take the digital video feed and convert it to component video which may not be to the media industries liking who outlawed component video because it is easy to use for copying purposes.
Overall it does not look very promising for an adapter that can take the iPhone 5 and make it work in the same way as the older iPhones with the 30 pin connector.