I feel like after the initial release when everyone is just checking it out the numbers are going to plummet. That said I feel like it will steadily find it's main audience and then grow again to a healthy number.
A lot of people who never actually played back then are going to check it out, realize it's a totally different game and probably bounce out after they realize they can't hit level 30 in a few hours. I think that will make the game better though as it will weed out all the people who never intended to actually enjoy it anyway.