Is it worth spending $10k on CD-only player today?

I'm not sure that it ever was.

In digital media sonic quality is ultimately limited by the finite amount of information on the disc. Playback equipment, no matter how good (or expensive) can only approach a limit imposed by the media. The information on a CD, 16 bits and 44.1 KHz sampling, is barely acceptable for audiophile recordings. The much greater information available on a DVD or SACD permits any decent DVD/SACD player to compete with the best CD players.

Presumably the answer to this question depends on the individual and their priorities. In my case the answer is yes, it is worth it to me. I want outstanding sound, in digital format, right now.

Not to me.

Yes. I would if I had the scratch, a larger income, or if I was more established in life. SACD isn't going anywhere unless you listen to classical music. I do, so I would likely consider the Meitner stack. I would not consider something with compromised redbook playback. I'd rather have a dedicated rebook player in that scenario. And I feel that is the crux of your question. Redbook is too ubiquitous. And as such would not fit morepeople's definition of 'obsolete.' Though there are many slight meanings of the word.

Although SACD and DSD is superior to redbook, redbook will likely be obsoleted by mp3 or something similar. And by something similar I mean something distributed as a computer file - either hi-rez (not likely) low-rez (more likely).

Like many others I was also in the same place. I have a large cd collection(6K) so I purchased the best cd player I could afford. I was also interested in SACD and purchased a mid price(3K) SACD player. While I love the sound of SACD( I have a little over a 100) I play my cd player most of the time. I beleive Redbook will be around for quite awhile and SACD may become a niche market if they don't pick up the pace with more releases and lower the price. So in other works YES it is worth spending 10K(if you have it) on a CD only player.