I’ve seen a few projects with their main/trunk-branch hosting a package with a .opam/dune-project file listing the version as unreleased. Their CHANGES file also lists the changes from the last release listed under “unreleased”.
Is “unreleased” something that is recognized by any of the build/release tools that gets automatically updated when releasing the next version?
For what it’s worth, “unreleased” is the suggested header for the section of the next release per https://keepachangelog.com. Since you’re not sure what the next version will be, it makes sense to not name it before then to avoid confusion. Not sure whether dune / opam do anything specific with it.