As for those who were already in the last beta or had signed themselves up, you need not apply again. Anyone previously accepted will automatically be invited into the new one upon release. Even with the new sign-ups, DICE has promised to give priority on original applications before getting to the new ones. Although the choice to include so many people makes us wonder how much larger this new beta will be compared to the original.
So when does this second beta begin? We're told to watch for further announcements in the coming weeks, although that makes it hard to guess on an actual date. We're hoping it'll be sooner rather than later, because our curiosity about the game's progress has become quite insatiable.