I was not aware of this. Interesting.
People are used to fanfiction being free and readily available online, not paying for it to be published. So, there could be interest in 'published fanfiction', but many people are likely content with the authors whose works they have already found for free, to be honest. That being said... obviously there is plenty of interest in the Star Wars expanded universe and Star Trek novels and the like, so probably there would be a market for Tolkien-based novels, comics, etc, as well.
Well, the phenomena of publshing fanfiction with "serialnumbers filed off", "binding fanfition" and even some third parties taking (stealing) popular fanfiction stories from fanfiction websites and publishing those in a print-on-demand fashion (sometimes also "rewritten" using AI) - as the copyright in their own countries is a more loose concept or not really implemented, especialy for foreign works - all this demontrates that there is for sure a market for them.
Sherlock Holmes stories - almost from the very start - had fanfiction stories called "pastiches" published [
https://bakerstreetbabes.com/pastiche-vs-fanfiction-the-debate-that-wouldnt-die/: "
Let’s make one thing crystal clear. All pastiche is fanfiction. Breathe into a paper bag and repeat: All pastiche is fanfiction. Anything written by a fan of something, inspired by that something, is, by definition, fanfiction. There is nothing inherently negative, suggestive of low quality, or second class about fanfiction. It’s been around for hundreds of years and will continue to be for the foreseeable future."], mostly with the blessing of the Conan Doyle Estate, but now, as Sherlock Holmes is wholly public domain, anybody can freely publish anything about Sherlock Holmes:
en.wikipedia.org
We can well expect similar for Tolkien's works.
But still, as New Zealand has the time advantage of 20 years against most other countries - its copyright period still being the old "death of author +50 years" (it has not joined the extention to "death of author +70 years"), imho it could very well make use of it.
[Generally differing copyright periods in times of worldwide shipping and easy border crossings are strange for books, as one can simply just buy/print-on-demand one while abroad in a place where it is already public domain.
Also, the copyrights for The Hobbit expire 1933 in the US (as it was published there before 1978, as such in a copyright transition period) while they are already past in New Zealand and will expire 2044 in the UK (and most of the EU and other countries). So there is a 11 year old gap when a theoretical US public domain Hobbit movie could not be distributed offically in some worldwide markets while the reverse is true for the LOTR books - a situtation which would encourages online and offline piracy.]