The Conan Doyle Estate is now finally responding to to Les Klinger's lawsuit to declare Sherlock Holmes in the public domain. They seem to be arguing that Holmes's character continued to evolve in stories past the 1923 cutoff year, and that Holmes's personality traits should not be separated out into pre-1923 and post-1923 versions.
To some extent, Holmes did change over many stories, but it was not a well-planned evolution, and only about 10 of the 60 stories were first published in 1923 or later. Some Sherlockians even complained that Holmes was in fact too different when he came back after Reichenbach Falls and that the mysteries were recycled and not as good in the Casebook stories. That's been the basis of Sherlockian theories to discredit the Casebook stories as spurious.
I personally don't want the Holmes that retired to keep bees, lost touch with Watson after 1914, and wrote about jellyfish mysteries. (In my fiction, I personally prefer to say "La la la! Not true! Watson was lying because they were together forever and had to protect themselves from the law.") So that's not the Holmes I want, and it's got nothing to do with copyright. We'll have to see if audiences will watch an old retired Holmes when the Slight Trick of the Mind movie comes out; Holmes is retired and mentally failing in that one.
I recently read an ebook called The Sherlockian, which is a fictional mystery set in two time periods. In the modern day, Sherlockian detectives look for a lost diary of Arthur Conan Doyle. Meanwhile, in 1900, ACD investigates a mystery with Bram Stoker, and I was highly disappointed that it was serial killing mystery. (I am sick to death of serial killers! They're the plot devices of lazy writers who can't craft a non-psychopathic motive for a crime.) Anyway, the mystery was supposed to explain why ACD finally decided to write Hound of the Baskervilles and resurrect Holmes, after ten years of avoiding offers from publishers. One of the modern characters claims that Holmes came back jaded and distrustful of policemen, and the whole time I was thinking, Wrong! Holmes is nicer to Lestrade in the Six Napoleons, and he takes a mentoring interest in young Inspector Stanley Hopkins, post-Return. Holmes was very rude to Lestrade and Gregson from the very first story. Holmes also expressed cynicism with the world, and he took justice into his own hands long before Reichenbach, such as in The Blue Carbuncle and Case of Identity. So no, Holmes did not have a consistent character evolution during the course of 60 stories, because ACD just didn't give a crap about Holmes, or Watson.
I'm still rooting for Les Klinger to win, and I hope the judge will make a ruling soon. One could argue that the fanwork of Sherlockians, writing both pastiches and interpretive commentary like in the Annotated Sherlock Holmes, were the real authors making any efforts to introduce consistency and character development to the canon. There were efforts to explain blatant contradictions, like Watson's marriages and Moriarty's two brothers with the same name. We cared more about making sense of Holmes and Watson's lives than ACD ever did.