The update is currently a manual update.
Originally it was planned to release as a so-called "forced update", which would force all players to download the new game files before being able to continue to play DragonSoul. Due to issues with the app stores, this was changed.
This means for now the update is not used by all players, and therefore the skins aren't yet unlocked.
Usually the update will be "forced" after a few days of being available for manual download. Kenshirou and me will try to keep you all updated on what this means for the time of the mastery skin release.