What’s Entering Public Domain in 2021: The Great Gatsby, Music by Duke Ellington

There are a few near-future scenarios that intersect in interesting ways:

The possibility of life extending interventions such that average life expectancy climbs first toward, and then perhaps past, the century mark (life-of-the-author plus anything starts to look ridiculous).

The possibility of uploading whether it is a true digitization/emulation or 'just' a simulation of a particular consciousness given enough data.

Cryogenic preservation and revivification.

Legal decisions on whether such events count as 'death' for purposes of copyright, debt, inheritance, etc.

Legal decisions on the personhood and potential emancipation of digitizations, simulations, emulations, etc.

Legal decisions on the criminal and civil culpability of such simulations etc. (if considered persons, or their owners if not) for their originals' acts (such as copyright infringement).

The copyright status of works created post-mortem by such entities, whether they are considered persons or not (such works might simply be considered or passed-off as 'unpublished', for example)

If nothing else, I'm pretty sure that there will be attempts to hack around any legal uncertainty with various permutations and combinations of corporate personhood, copyright assignment, work-for-hire agreements, and smart contracts to get to some desired result regardless of how the legal environment changes, but those still might fail in 'interesting' ways.

All of which is to say that we might very well get in to a situation where it is possible to provide incentives for the creation of new works by dead authors, legally speaking. At which point the public, and the public domain, will be well and truly screwed over.