Though there is a merger between Ymir and Yggdrassil in the future, players who transfer all characters on a server to another server will be able to do so with relaxed transfer restrictions.
With the exceptions of Brisingamen, Mjolnir, Slepnir, Megingjard and cases where it's obvious that the move is being done for destabilizing the destination server's markets players will be able to bring all items and zeny on the characters over. Storage will still not be transferred, the items must be on the characters being transferred over. All characters must be transferred at the same time, if you only have one, two, three, etc. characters on a server it will still count.