I doubt that Kala will be out of LTL. If anything, I wouldn't mind that she continued her cunning ways from outside the PN. It'd be kind of cool to watch a power-struggle between Kala and her so-called "brother" whom she has some sort of obsessive compulsive hate-love thing for.
Honestly, I don't mind if BH is kept away for a bit longer yet. I know it's a loose end and I really want the answer to who it is, but right now I feel like we have enough villains as it is. I want to see Naku opening up to D about her past, and I want to see her past catching up to her and forcing D to fight for her somehow. You know?
They can sneak in BH and have him/her connect with Kala in her evil schemes once she's gone from PN, but I don't want the focus on BH just yet. We've watched Naku deal with what D was and has become, we've watched her accept his past and know him. It's time for D to get to know about his wife's past. I want Morey to return as a potential threat once Chaskar is out. If he's ever out, that is.