It was announced that today that any names that conflict will either stay the same (for the most active user), however the other users will have a special character added to them.
E.G, All users aclled Jack would either be Jack, Jack#, Jack$ and various over symbols.
Habbo also deleted all accounts that had no Credits, Furni and had only logged in once, so alot more names will be avaliable.
Check out the full story here: http://www.habbo.co.uk/articles/1096-whats-in-a-name