With so much time before Wrath comes out it'd be easy to get toons on any new account up to 55 if you started them soon...but I transferred my tankadin to a new account recently so that he could tank for all the shammies and I fully expect to be able to create a DK on his account. I don't really see it as an exploit even if the real reason you are transferring toons around is to have more DK's. Blizzard makes money from it and I doubt they'll prohibit it plus there is the transfer cooldown, it's not like you can move a toon, create a DK then move that toon again the next day. I guess you could xfer a DK to another account.