Are we talking typical hi-fi? If so, then yes, the argument is probably moot. However, typical hi-fi was not the impression I took away from the article. What I was reading between the lines from the author was what is "possible" with newer, extended formats.
It was my experience in my early days dabbling with live recordings (high school bands and choirs, church choirs, rock bands, etc) that anything I recorded "live" or in our makeshift studio almost always sounded superior to what was generally available on the record racks in the stores. Musically, commercial music was original, that's for sure, but the sound quality we captured was vastly more alive, open, dynamic and realistic.
However, there were some quarter track recordings we sometimes purchased that sounded vastly superior in comparison to the LP version. Believe it or not, Crosby, Still, Nash and Young, Deja Vu was available on 1/4 track reel-to-reel and it sounded much better than the LP when played back over our Telefunken reel-to-reel, and HH Scott receiver!
In the early 70's we once had a visit from a professional recording engineer who brought in his half-track master of the same recording that was in our record racks. It was so vastly superior that we couldn't believe it was the same music.
There are plenty of examples of loudspeakers with FR beyond 20K, including the Revel Salon 2, Vapor Cirrus, Merlin VSM, and virtually all the Dali's, to mention a few. With your background in studio work, recording, (etc.) you are already aware of several microphones available with solid capabilities beyond 20K, including the Earthworks QTC30 (~30K), Sanken CO-100K (~100K), the Sennheiser mkh8050 (~50K) and mkh800 (~50k). (Which of these have you already used in conjunction with AD systems capable of capturing these extended frequencies? Can you let us in on your own personal experience and what differences you observed?)
CD and LP comparisons? Well, besides the one's above, you're experienced enough to have heard some of the better LP based systems and know what sonic levels can be achieved from these and other analogue mediums. Speaking of typical hi-fi, personally, I'll take the sound quality from a $5K - $10K based turntable and some of my early Sheffield labs discs over 95% of the digital media and DACs almost any day. You can complain about the music on them all you'd like to but, the sound from these discs on a high-end system, or a typical hi-fi for that matter, is still highly regarded. (Although I'm starting to hear some similar sound quality--thankfully--from recordings from the new Bravura Records.)
To me there's a lot left for discovery. If the CD is it, then, I'm just gonna have to attend more concerts. There's lots of musical content above 20K at a live symphony.