The routes add-on is only used during initial installation. You do not need to install it again before you upgrade.
EDIT: I can reproduce vw_wiki_upgrade_error when accessing the wiki admin tab after installing the VaultWiki Routes add-on only if I have not uploaded the vault/install/lib directory. If the directory is present, the error correctly reads "The wiki has not yet been installed. Please run the install script." However, even if the vw_wiki_upgrade_error is there, the navigation link "Run Install Script" still works correctly for me.