It means that subscribers will basically be able to create an (almost) unlimited number of characters.
This means that across every server, we were originally allowed to have 50 characters total. With 12 per server. Now, apparently, we can have more then 50 total characters in an upcoming patch. Who the hell has enough time on their hands to play 50 characters? Or more now...
Do we know how many we can make per server? I don't cross servers but I'd like to have more alts :P