An IBM i-to-IBM i migration does not automatically require rewriting RPG applications. Check the program objects and their dependencies against the target IBM i release before deciding which changes are needed.
A release change can require program conversion or a newer vendor build. Older compiled objects and missing source need special attention. Moving an application from a different operating system is a separate conversion question, so it should not be treated as an ordinary IBM i save and restore.
Review applications and program objects with the installed-release upgrade guide before assuming an application needs a rewrite.