It's 70 in the US now. From the US Copyright Office: "As a general rule, for works created after January 1, 1978, copyright protection lasts for the life of the author plus an additional 70 years. For an anonymous work, a pseudonymous work, or a work made for hire, the copyright endures for a term of 95 years from the year of its first publication or a term of 120 years from the year of its creation, whichever expires first. For works first published prior to 1978, the term will vary depending on several factors."
Yes, I know. The requirement of the Berne convention is 50 years after death. The US goes twenty years beyond that.
If AI is the author then what?
Nothing AI created can have copyright under current law.
In the US, indeed. But in the UK the runner of AI can hold a copyright. Which I think is stupid but that's hardly the first dumb copyright thing.
For something like img2img with Stable Diffusion, if the starting image is copyrighted by someone else I'd expect that the output image is a derivative work of the starting image.
The question is about new copyright in both cases, not subsisting copyright. You hold the copyright to the elements originating with you in a derivative work.
The author is the one that records it, not the tool used to create it.