KI has stated before that they won't ever add another slot, sorry bro
They haven't stated that, but they haven't stated that they ever will, either. It's completely up to KI, but I don't think they'll do it unless they profit more from it than they currently do with second accounts.
KI is known to change there mind after saying no a few times. The last thing I heard they're talking about adding the 7th wizard to an account. KI may be waiting for more players to agree.