as you are not able anymore to choose your own accountname, while creating your account, you need to create a profilename which is used somehow as an alias.
I know it was asked very often, why the username can't be changed and I remember it was an issue with the mapping of Playlists <-> Account.
Now, with this new concept of creating profilenames insted of usernames, this issue should no longer be an obstacle in implementing a feature which allows users to create or change a profilename right? Even for someone like me, with an account from 2012, where the username is not a random number.
Creating/Changing the profilename would fulfill the user's needs, as the only reason someone wants to change his username might be, that he chose a quite anonymous username (like me), or just a "stupid" name. I think, most users wouldn't have a problem if you still need to login with the old real accountusername. It's just that many would like to change the name, others are seeing.
(and no, connecting to Facebook is not an option 🙂 )
To sum it up, will there be a way to create a profilename for an existing account or is this not planned in the near future? One could at least suspect, the developers are heading to that direction.