I have been using the auto localisation update extension https://github.com/cividesk/com.cividesk.l10n.update successfully for a several years. One of my frustrations though is that every time I upgrade a CiviCRM version I have to manually create the l10n folder. It would be great if this folder could just be included in the standard distribution of CiviCRM Fetch and install localisation files should really be a core component now.