Using a GPU for audio makes a lot of sense. That said, the original TrueAudio was not really about that, and it didn't really take off. The API was only implemented in a handful of titles, and it required dedicated hardware that they have since removed from their latest architectures. It was not about using the extra horsepower of the GPU to simulate sound, although they did have ideas for “sound shaders” in the original TrueAudio.
TrueAudio Next, on the other hand, is an SDK that is part of AMD's LiquidVR package. It is based around OpenCL; specifically, it uses AMD's open-source FireRays library to trace the ways that audio can move from source to receiver, including reflections. For high-frequency audio, this is a good assumption, and that range of frequencies are more useful for positional awareness in VR, anyway.
Basically, TrueAudio Next has very little to do with the original.
Interestingly, AMD is providing an interface for TrueAudio Next to reserve compute units, but optionally (and under NDA). This allows audio processing to be unhooked from the video frame rate, provided that the CPU can keep both fed with actual game data. Since audio is typically a secondary thread, it could be ready to send sound calls at any moment. Various existing portions of asynchronous compute could help with this, but allowing developers to wholly reserve a fraction of the GPU should remove the issue entirely. That said, when I was working on a similar project in WebCL, I was looking to the integrated GPU, because it's there and it's idle, so why not? I would assume that, in actual usage, CU reservation would only be enabled if an AMD GPU is the only device installed.
Anywho, if you're interested, then be sure to check out AMD's other post on it, too.