I doubt the author will sue.
But if you read that link --- and remember we are only dealing with the [ somewhat ridiculous, thank you Sonny Bono ] copyright laws of the USA, every other country has their own laws, however conforming to agreed group laws --- he is out of copyright clear and free.
The legal case of Klinger v. Conan Doyle Estate that settled the claim actually rested on an interesting issue, whether a copyright claim can persist on a character even if the works depicting that character have fallen out of copyright. The defense of the Doyle estate went something like this: sure, Arthur Conan Doyle’s stories are now at least 90 years old, but other stories about Sherlock Holmes are still under copyright, therefore Sherlock Holmes is still under copyright.#
link above.
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The ruling, issued by Richard Posner of the Seventh Circuit Court of Appeals, affirmed a district court ruling, last December, that the characters were no longer protected by American copyright, and so could be used without paying any permission fees.
NYTimes