Whatever happened to HDCD?

They are issued frequently. Joni Mitchell's two most recent are HDCD. Playing these the Lindemann is without peer.

I think you are correct that HDCD do sound better. The technology seems buried buy its new owner. However new formats like SACD and DVD-A seem to be getting all the attention. If all CDs were made like XRCDs or HDCDs and recorded correctly there might not be a change. That and the desire of the manufacturers to find a non-recordable system and discontinue the royalties paid to Sony/Phillips for CD technology (though I think this is running out). Many companies don't want SACD to succeed because it will further inrich Sony/Phillips.

Not being in the music business, I don't know why HDCD is not used more. Perhaps its not being marketed well by the technically inept boys in Washington. As a consumer, I own about 20 and they sound pretty good to me. I hope it doesn't disappear. HDCD releases are still coming out. Recent ones (last year) include The Mavericks (self titled).

Yes, Microsoft now holds the patents for HDCD from when they bought Pacific Microsonics. Microsoft is trying to integrate it into online media.

If Sony/Philips had also owned HDCD, it would probably be part of every DAC chip made today, and would have been the standard long long ago. HDCD does not have the compatibility problems with Redbook like SACD does. HDCD is more like an enhancement or upgrade to Redbook, rather than a totally different technology like SACD. But SACD is the one being pushed hard because Sony/Philips does also own that (which is not catching on because of the added cost).