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

I say no. No matter what the voodoo inside the player, the bottom line is that redbook CD just can't reflect all the advances in recording technology in the last 20 years. Surely anything worth listening to will eventually be released on SACD. I was playing with the idea of a mid- to upper-end CD only player to suppliment my SACD player, but I'm going to give it a rest for awhile. I'll bet expensive CD-only players with today's esoteric innards will come way down in price in the next few years.

I asked the same question, and my answer was "yes". My rationale is that there is an enormous amount much redbook product out there, and the fact all the new releases support that format means obsolesence just isn't an issue. I remain unconvinced about SACD's long-term success as a format.

Anyone who feels redbook is comparatively unlistenable hasn't heard some of the really good players/DACs out there.

This really begs the question "how many redbook CD's do you have?" If your collection is large (i.e. in excess of $20-30k) and growing, then a good redbook player may be in order. (I do think $10k is excessive however...)
If not, wait and see -- if nothing else, mod your existing player.