The biggest evidence is actually the ChrRaces.dbc database file, which is a database file that contains the full listing of playable and non-playable "character races," as well as flags to determine whether or not they're playable, and, if so, which character creation and selection screens they use and what their customization options are.
None of the strictly NPC races are flagged with character creation details; not even the confirmed Kul Tiran races has character creation details yet.
However, back in early February, the Vulpera race was added to the ChrRaces.dbc database with flags for character creation and selection including customization options and more importantly the Horde character creation glue screen (ID 623714, the Orgrimmar backdrop) as both their CreateScreenFile and SelectScreenFile ID.