How to link a view to the current language with a no results fallback to the default language?
Check out http://www.webomelette.com/drupal-views-pre-render-alter-display, u should be able to use hook_views_pre_render() in a custom module and check your result set before rendering.

In the case of no results, change language to sites default in the view object, although im not sure that this hook will trigger your new query to run and bring the default lang contents, but its a start!

http://drupalcontrib.org/api/drupal/contributions%21views%21views.api.php/7