I don't believe PropertyPlaceholderConfigurer was meant to be used in an I18N scenario. In this case, you probably want to consider something from the resource bundle interfaces like ResourceBundleMessageSource or ReloadableResourceBundleMessageSource. In that case, you may need to find another way to set the property on your beans as it won't work in the context of the XML config file processing.
Why does one want to inject multiple i18n resource bundles. Should that not be part of implementation.
Unrelated but, I was just curious.
As I understand, PropertyPlaceholderConfigurer is for injecting the application properties. I guess org.springframework.context.support.ResourceBundleMessageSource should be used for loading i18n messages.