This issue has been reported by French IGN:
A previous issue clarified why the scope is set ISO 19115:2003 and not to ISO 19115:2014. A possible clarification was that "the current WG charter proposes to work on the ISO19115:2003 version, as the 2014 version of the standard does not have an XML syntax yet (expected 2015). Also, the INSPIRE Metadata technical guidelines are based on the 2003 version. Consequently, descriptions of spatial datasets, such as those in the INSPIRE Geoportal still follow the 2003 version".
However, French IGN points out during the GeoDCAT-AP public review that the XML Schemas defined in ISO 19115-3 are now stable enough to be used.