Storm Audio has a processor that will do it via AES/EBU. Also, there are JBL processors with Dante outputs.
They exist but they are limited to 16bit/48KHz output due the idiocy written in to HDCP agreements amongst other things.
It would be so much more efficient to separate out the HDMI switching, decode in to discrete channels, speaker processing (including room correction) etc and connect each bit together with a single cat 5 cable.
Thank Hollywood paranoia for not being able to do this in the consumer space.