Nope when they're done reworking then they start adding and tweaking.

I personally think the reworking will be done around the time of patch 1.21 when the job system is released. From the change plan Yoshi posted most of the major restructuring will be finished around about then with other stuff ongoing, but the ongoing stuff is the kind of things MMO's are always constantly tweaking.

I'd say given that it took 5 years to develop the initial incarnation of this game, rebuilding it in just over a year is pretty impressive. After all, it took Blizzard something like 2 years just to develop Cataclysm and that mostly only changed the games map with a few class tweaks, S.E have had to pretty much redesign all the games mechanics from the ground up, and from what it would appear they will eventually be changing the map too since everyone has been complaining about the 'copy&paste' enviroment.