Recently I converted some existing libraries to use dune as buildsystem. Since a while dune can create <package>.opam files from dune-project. Since a dune-project file is required anyway it feels wrong to maintain the opam info in two files. Therefore I think *.opam files should not be kept in SCM.
Does opam make any use of the *.opam files in a SCM? I think it uses just the files downloaded from the opam repositories.