Here are the differences in the DTDs, checked against the spec. (Just a cursory look at the spec, so please correct.)
There are missing sections: please review the list, and put your name in [...] by the item that you should own, then file a bug to fix it, and fix it.
DONE metadata casingData
DONE calendar: monthPatterns cyclicNameSets
DONE otherNumberingSystems: native, traditional, finance
DONE: [Mark] need to fix description in bcp47 that native must be decimal.
DONE [Mark] collation reordering
DONE [Peter] time attribute (Some examples had time=; they were only for the deprecated (in ldml) weekendStart and weekendEnd elements. Deleted the examples.)
DONE [Yoshito] attributes: extension, description, and since (the latter new on 'attribute')
NOT-DONE [Umesh] gender (of personList)
DONE territory containment - deprecated attribute
DONE plural rules can be either ordinal | cardinal
DONE mapTimezones have new attributes for version info: typeVersion otherVersion
ALL DONE (with general note)