EAD 2002 can support geocoding of a sort.  In our finding aids, we use "geonames" as a source and the Geonames ID as an "authfilenumber" in the geogname element.  This allows us to link to cities, regions, or countries defined by Geonames, and we can extract latitude and longitude directly from it.  It appears that EAD 3 will support latitude and longitude explicitly entered into attributes in the placeentry element, as well as @vocabularysource for the full URI.  I am not sure the relation of geogname to placeentry in the new schema.  Someone from the committee will have to chime in.