I'd say 3-4 weeks think about it , beta will have as much as 5 million people playing , a ton of issues / bugs will be sent into support for them to fix and with 5 million people I Doubt it'll take long before we find and stomp out all the issues which will bring the beta to an end . So my guess is 3-4 weeks . 4 weeks because they are treating this beta as a full game launch so it should be longer than usual .