I think that characters on that are "new" will be in the "new" system for x days (say two months). Then after that the character is switched to old. This would be ideal for some sort of ladder setup.

But let me note - if your character switches from new to old, it won't be able to join new characters games anymore. If this were true you would have to mule all of your items over to new characters before they switched to old, in order to keep them on "new" chracters.

-FunkyDo