It's all about profits. Nothing else!
I read somewhere about a year ago that the teams and resources (including all R&D) for the Phaeton were being slowly 'realigned' to focus on their more upscale niche: Bentley.
This may indicate that they are planning to eventually get rid of the Phaeton (or maybe just keep the name and dress up an Audi A6 with the VW badge to clearly steer away from A8s playing field).