On Tue, Nov 26, 2019 at 4:42 PM Eli Zaretskii <eliz@gnu.org> wrote:

> Could that disrupt noninteractive calls?

Yes, that's why added the notice in NEWS in the "Incompatible Lisp Changes".

But, on one hand, programs should perhaps be using
switch-to-(prev|next)-buffer. AFAICS, next-buffer and previous-buffer
aren't even documented in the Elisp manual (they are briefly mentioned in
the Emacs manual).

 And on the other, if code is using (next|prev)-buffer, silently getting
the same buffer is likely a subtle bug anyway. At least now they get notice.