There's a lot of items stuck in user shops, users that have not been here a long time and their UN is up for clearance and use again. But what happens to their shops and the items stuck there?

Nothing. The stuff continues to just sit there. They used to delete accounts, but haven't done that in years. Other than the name change, nothing else gets changed on their account (ie if their username is John, their new name will be John154687).

Since old inactive accounts aren't deleted anymore, all the stuff is going to stay in the inactive users' shops

Thanks both for answering. Seems such a shame though and it messes up prices a bit...