If you are using the built-in functionality to rename a variable, then that renaming will follow through for all historical forms as well.

If you are adding new fields to the form with different variables, and removing the old ones, that will not.  The old variables will remain in the history, but the preview of the completed forms will not show them as they are no longer on the form, and will instead show blanks for the new fields you have added.

P.S. You might want to edit your post and change it to a question instead of a discussion so that you can mark it answered once you are satisfied with response(s).  Thanks!