As per my previous hopes, the Traxxas TQi Radio (6507) is indeed available as a separate item very soon (early 2012).
The TQi was released with the new Traxxas XO-1 Supercar.
For £150 you can get both the radio and the iPod/iPhone dock, and the 6518 5-Channel receiver, although no solid information for if the telemetry sensors are included.
Also no evidence yet of the availability and price of the lone docking station upgrade to allow owners of the XO-1 to get the full benefit.
The 6518 receivers are also available for a reasonable £45 for any additional models you may have, again, unsure if the receiver comes with a full kit of telemetry sensors.
Interestingly it first appeared that the docking station and the radio itself had their own independent power supplies. The radio states that it requires 4 AA batteries, and the dock also requires 4 AA’s but also has the ability to use the Traxxas 3037 NiMH hump pack to provide the juice, and will also keep your Apple device charged up.
This make would sense in a way as the iPhone element is not a critical element of the system so you wouldn't want it reducing the radio power to nothing and rendering everything unusable. At least with the radio still powered you can continue to operate your model.
Alas, studying the gallery images appear to paint a different picture, and several in particular demonstrate that the batteries are stored in the bottom of the hand grip.
I'm certainly leaning towards getting one of these for release day and see how well it all performs. If it lives to expectations and has an all-round improvement on the R/C experience i could be seriously tempted to make it a single system and swap out all of my Spektrum kit.