There's been talk of several characters who have been confirmed, some who haven't. Most of the ones that we have heard rumors of are either rumors, or they have minor roles in the show.
Here's the characters I know of, that have been talked about, and are confirmed to have larger roles than just a cameo in Season Two.
- The Herald (he's already appeared in Season One)
- Batgirl (Same as above, but probably more likely than the Herald to become a member of the Team, even if it's a brief stint.)
- Blue Beetle (I think it's actually confirmed that he WILL be joining the team, but don't hold me to that.)
- Beast Boy (Already getting a larger role, but too young for the team in my opinion.)
- Lagoon Boy (I think he's confirmed too.)
- Bumblebee (She's already appeared, just like The Herald, although neither seem to have become superheroes.)
- Static (This one is a fan favorite, and there have been rumors due to a confusing interview, but it might not happen.)
That's 7 characters. Chances are, not all 7 will actually join the Team, but if they do, are we looking at two seperate teams? Maybe an Alpha Team and a Beta Team? Because that would make it 14 people on a team (without Red Arrow). Two teams, or are we going to rotate rosters? Or are we looking at a huge team with very little development?
Hopefully, it's not the last option. They haven't let us down so far, but who knows?