FYI: The new overworld isn't out yet still. It says they've been running into various problems as they get close and think they can release, but then it's too major to release. I'm sure they know of the bitching that many whiny PC gamers tend to do if it's not perfect.
The whole time I've been amazed at the game they made with such a small team. But it has been getting a bit long waiting for open beta (I don't need it personally, but others are waiting), then that was put back with the new overworld announcement, and now even that is going to be much later than they planned.
At first glance, the new overworld seems more of just an improved camera to a game that is already 3D and has a sort of camera like in Wow, etc, although very primitive right now. But it seems it will be much more than that and should relieve some of the tedious and same gameplay. I thought I would've liked to seen skill and item rebalance/changes, more zone 3 quests, new class, better PvP options, etc before this new overworld (since the overworld seems to have pushed most of those other major things back), but I think the overworld really has a chance to drastically change the game for the better. And it'd be better to make the change now then when the game is about ready to release where it might be unfeasible then.
So, just a random guess, but people waiting for open beta will have to wait at least another month, if not two or three (just a random guess). But it's still worth a shot trying to get in the closed beta. They are gonna wanna stress the servers with the new overworld (which will be instanced still but with MANY more players) and maybe if people have been leaving the game they will want to bring in more.
edit: Holy **** boys! It's out! Well they have another server setup with it on, so for now the old one with all of your characters is still there, or you can start over with the new overworld (only zone 1 so far). I'll be able to check it out in an hour or so!