PlanetSide Universe has a post summarizing plans for beta testing of PlanetSide 2, bringing together details about the MMOFPS sequel from various posts and tweets (thanks Matthew). They say external testing is kicking off this week, and outline who is being granted access to the beta, noting that PlanetSide veterans are already in line for keys. They also explain that unlike many "betas," they are actually using this testing session to improve the game, not just promote it:

Beta testing is a critically important part of our development cycle on this project, we may be asking you to only play on tanks for a play session, or only play aircraft. We are doing true beta testing, not just a game demo and we implore those of you who are invited to understand and respect that. Things will break, the server will be unavailable sometimes, we will cancel scheduled tests when we find something that breaks before the test starts. All of this will help us make a better final game.