I heard that the amount of time required for a work to be in the public domain has been extended. If you want your novels to be in the public domain as soon as you die, how do you do that? And can the publisher become an impediment to that?
Strictly speaking, at least under US law, you probably cannot put a work into the public domain. (The point is not finally settled.) But you can release a work under a sufficiently permissive license that the practical effect is the same. the CC0 license from Creative Commons is one such license.
An author can at any time release any or all of his or her work under such a license, unless s/he has contracted not to do so (as by giving an exclusive license.) It could be done in a will. That would be the way to make such a release at the author's death, although it would not be effective until the will had been probated, usually some months or even years after the death, depending on the jurisdiction and the complexity of the author's estate, and how quickly the executor acts.
Or an author could simply publish such a release when s/he knows that death is imminent.
A publisher will generally be opposed to such a release, as it will significantly reduce any potential profit the publisher could make from the work. Most publishers will demand an exclusive license if they are to pay for and publish a work, at least exclusive within some geographic area. Once an author has contracted with such a publisher, the rights may not be released freely to all, until the license to the publisher is terminated or expires. (To do otherwise would be to breach the contract.)
The term of copyright for new works under US law is now the life of the author plus 70 years, which it has been for quite some time (or 95 years for corporate works or works of unknown authorship). Several other countries have the same term. Some have life+50 years.
A release under a free license will generally make it harder to market the work, or obtain money for it, if the author cares about that.