Robert, you need to ask this question here in A/V Sources -- hardware-related question, hardware-related area.
As to your question, no actual specifications on an HD DVD player or a Blu-ray player have been released. According to Toshiba, the company still is shooting for a fall 2005 release of its HD DVD machine. One would assume that, yes, an HD DVD player eventually will be able to decode/play DVD-A as well as SACD. But do not expect any of Sony's Blu-ray machines to play DVD-A.
I thought I read that the new Playstation with support Blu-Ray and SACD playback. You may want to do a search. Sony does not support DVD-A, although there are some BMG releases. Universal has announced support for Blu-Ray and it would not surprise me if hi-rez PCM via Blu-Ray will be next. So you may want to hold onto the Pioneer until it sorts out
Although (yes, Phil) PS3 has been announced to support SA-CD playback--per Jack's mention of the absence of final specs--we don't know yet if the Blu-ray audio spec will include SA-CD's underlying technology, DSD. (Might Sony further abandon SA-CD as a format and just enable BD to carry a DSD bitstream for hi rez audio?)
We do, however, know that HD DVD supports DVD-A's underlying codec, MLP.
Yes, hang on to the 563. And hope it doesn't take Pio so damn long to come out with a hi rez aud/hi def vid uni player.
HDMI will allow DSD bitstreams pretty soon, so if the PS3 or other Sony device does not have DSD decoding you could always try to find an outboard DSD decoder. I'm sure there will be some around.
24 bit/192 kHz LPCM for 6 discrete channels, at least (maybe 8 discrete channels too, but I haven't seen the final Blu-Ray specs; possibly it's 24/96 LPCM for 8 channels) is nothing to sneeze at if that's the future (at least for 10 years or until the next new thing comes along).
I too want an all inclusive player (sans HD-DVD since I have a hunch it will be the HD format that folds its tent first, but includes DVD-Audio support) that will at least act as a decent transport to get the bits to some other A/V decoder.