Perfecti0nist wrote...
The only old character that could be bisexual is Jack. She talked about a threesome and it seems like she doesn't care who she sleeps with.
Jack is no more explicitly bisexual than any other character. Yes, she did participate in a threesome with a male and a female, but even if Jack had a healthy attitude towards sex -- which she doesn't -- a willingness to engage in new experiances does not define her.
Also, Jack certinally does care who it is she sleeps with. Which isn't to say that she's not willing to sleep with someone she dislikes, but rather that sex is one of the means by which she's able to establish her opinions of others. If she didn't care, she wouldn't be so upset about Shepard using her for sex. Again, not a healthy approach to sex, but she's a complex character.
All that isn't to say that Jack isn't bisexual. Rather, her sexulaity is somewhat undefined. Granted, I choose to interpret the culmination cut scene of her romance chain as being rather chaste, so perhaps my perspetive is a bit different.