1 The judgments appear to be here and here. As summarized here: "copyright protection had expired on all elements of the Holmes canon that were first introduced before 1923 — including the characters of Holmes and Watson. The ten stories of the Case-Book of Sherlock Holmes, and the "increments of expression” unique to those stories, are still protected by U.S. copyright."

2 As for trademarks, according to this site: "While the Doyle estate contends that it owns the Holmes trademarks and, therefore, can control how (or indeed if) any "unsanctioned” projects are marketed and merchandised, it’s important to note that’s not necessarily the case. A trademark search shows that in numerous instances, the estate has merely applied for the marks; Klinger said in January that there will be "substantial opposition” to those applications."

3 Doki still submit magnet links (for e.g. Barakamon). They work quite well and may never need a particular tracker again (such as Nyaa).

4

I think that it's probably too late for the Doyle estate to gain trademarks on Holmes et. al. And if they did have them, arguably they've lost them by now because they weren't vigorously defending them.

And once you've lost a trademark, it's gone forever.

Example: A lot of people don't know that "Aspirin" used to be a trademark of the Bayer corporation. In the US it lapsed into generic use and Bayer lost control of it. But in Canada and Europe, if you buy "aspirin", it will be Bayer. Everyone else's product has to have a different name.

Kimberly Clark almost lost control of "Kleenex". The Xerox corporation almost lost control of "Xerox" (which in common use was a synonym for "photocopy"). CocaCola was perilously close to losing control of "Coke", which is why they clamped down in the 1970's, and why if you order "a coke" in some places you'll get asked, "Is Pepsi OK?"

I would venture to guess that 99 times out of 100 the customer says "Yes". As a practical matter CocaCola really should have lost control over "Coke", but I guess they caught onto the peril soon enough and avoided that fate.

Trademark law is a real black art.

5 I read a short sci-fi novel once where copyright lawyers were basically the superhero ninjas of the future.  Can't remember the name, though.

6 It's... not really clear, the extent to which you can use trademark to pick up from an expired copyright. Most cases are pretty open and shut since the various copyrighted works are virtually all owned by "estates" which don't use the characters in other trade. On the other hand, Disney is hell-bent on making sure that none of their characters ever go out of copyright in the first place, which you wouldn't think would be a big deal if trademark offered them the same protections...

At the same time, clearly Disney does use the Mouse in the sense that we'd expect a trademark to be used, as a general company mascot, so it's not clear that the moment it expires, you could immediately start flogging Mickey plushies without Disney's involvement.

This sort of thing is why lawyers can demand so much money - you get areas of the law where the real answer is "it's the way you want it, if your lawyer is better than their lawyer".

7 Similar to "Coke" and "Kleenex", "Formica" - a popular name in the countertop trade had to fight hard and almost lost the copyright. Sort of a victim of its own  success.

"Corian" was close to going the same way, but DuPont learned from Formica Corps. labors.