I'm doubting Joker is gonna be on the team. He'll probably be the antagonist, or seen in lock-up in Arkham. He's a terrible candidate for the Squad.
I sincerely hope they go with the old fat Amanda Waller rather then the toothpick thin supermodel she got recast as.
On the issue of Joker, fridge logic says it should be either a Hannibal Lecter-style caged beast who ARGUS will have to make deals with for information to progress in a mission or that ARGUS is fed up with Batman upholding his one rule for the one person he hates the most and they're just gonna take him out themselves. If Quinn is written as 'the rookie' and Deadshot as the crude, paternalistic team player, then most of the tension I'm guessing will be if Quinn encountering the Joker will trigger a relapse. Either way, if there isn't a cameo of Deathstroke by Ron Pearlman or Manu Bannett, I will riot.
Harley Quinn maybe bi-sexual with Poison Ivy?
Didn't know that. So is Poison Ivy also bi, then?
Since I am pretty sure she loves to hit on Batman and other men, no?
Yes. That's what bisexual means. She even dates a guy in the New 52, a day after she slept with Ivy. (You don't see sexy bits but the writers did confirm that they simply are not hung up on monogamy).