There will be an archive update soon but the only thing that I know of that is getting updated/added in the new Legacy Armor's 3 nonetheless, There will eventually be an archive update.
First off; Don't go around saying that we are getting something soon. If we ever get anything the GMs will announce it within patch notes or a post saying we are getting such an update.
Second; We just got an archive update. This update took us forever to get. I doubt we will get anything big soon. If we do then it will be announced in patch notes.
Third; As already stated by minuzaki; some costumes are just not archiveable as they are EN version only. This is something we got to live with for now.
As much as I also want an archive update; I would rather see other bugs fixed. At the end of the day the devs just give us the content. We can give them nudges and ideas, but they decide in the end.