Based on the docs, it'll still be 48kHz sampling rate on the SPDIF outputs, but it'll be a 640kbps DD bitstream, not the 448 or 352 stuff we get on DVD or ATSC. So still has the opportunity to be better than what you are used to today.

DD+ compressed is not outside the bitrate capability of SPDIF, and while Dolby could probably care less, I doubt any format with DD+ encoding, other than ATSC broadcasts when they go that route, will be configured to allow any DD+, TrueHD, or DTS-HD audio to go over unencrypted channels, decoded to multichannel PCM or still compressed.