This is scheduled for Feb 16th.
this is enabled on test.wikidata.org. we plan to enable it on Wikidata on February 16, and in the next couple days after to convert properties to the new data type.
see https://lists.wikimedia.org/pipermail/wikidata/2016-February/008140.html for more technical details about the new data type
https://www.wikidata.org/wiki/User:Addshore/Identifiers has information on which properties to convert and discussion is there.
@note when converting properties to the new data type, we should run rebuildPropertyInfo.php --rebuild-all --force (if we have trouble with caching and stuff like wbgetentities not reflecting the change in data type on items using these properties)