Check the latest dev blog from Arenanet as Jordan Massey tells us about the role of squads in world vs. World combat.
Joining a squad is just as easy as sending a whisper or a party invite. Simply select a teammate and right-click their portrait. If they’re in a squad, you’ll see an option to join their squad. Click that and you’re in! The commander doesn’t have to approve your request—you can join and leave freely. It doesn’t matter whether you click on a commander or a squad member. You’ll join the squad as the person you clicked on, so you don’t have to worry about chasing down a commander in order to join a squad. In the party menu on the quick-launch bar, there’s a small squad panel. From there, you can leave the squad you’re in if you want to join a different one, or if you’re just done for the day.
Source: Role of a Squad in WvW