I think it's impossible to answer this question - which isn't to say it isn't fun to ponder! - given there's still so much we don't know about the characters (or, in the case of SH they don't know about themselves), many of them have contradictions and tensions in their characters which can send them bouncing around the grid (a good thing in my book), and most of them seem to have the potential to change depending on what happens.
My take so far, though:
Astarion: CE - He's selfish and enjoys a laugh at others' expense. He's obviously had a crappy couple of centuries that have understandably left him bitter and keen to have his time in the sun, but frankly I can see him having been a crooked magistrate happy to take backhanders even before he got vamped. I can imagine him moving towards a more neutral alignment if he can come to trust the party and let go of his anger at Cazador, but can't see him moving a long way from the bottom right of the grid.
Gale: CN - he'll not harm folk on purpose and even will help them and want the best for them, but magic comes first and I don't get the sense that he's cared much about collateral damage in the past. And he's not one who is going to care about the laws of the land or order, he seems to care about freedom, knowledge and again magic. But he's had a horrible shock and I think so far it's made him more considerate perhaps due to his own loss of confidence, and depending on how things go with Mystra and the orb could move more in a CG/NG direction, stick at CN or, if things go badly, even slip into NE/CE.
Lae'zel: LE - authoritarian and sure her society's rules are right, uncaring and bullying towards others. I can see her becoming more chaotic if her faith in her society's rules is shaken, and possibly less evil if she can build positive relationships with the party that feel very different from those she had with other githyanki. Or just stubbornly sticking to her own groove!
Shadowheart: NE/NN?- she seems to believe passionately in her religion, but though her goddess is evil will try to justify the faith as good for people (stripping away lies), and she doesn't want to care about people but kind of does a bit, though not enough to personally choose to go out of her way to help them. She also seems to be happy to stir and try to cosy up to our main character and undermine their relationships with others. Possibly we really are building a friendship, or possibly (more likely) she's manipulating us for her own ends. On the assumption all the friendliness is an act, I'd go for NE, but in the absence of her memories to ground her that she's currently being pulled towards NN. But all bets are off when she gets her memories back.
Wyll: CN/NG - sounds like he was brought up by a crooked, selfish father and, while despising his father, Wyll himself learned to be crooked and selfish just in a different way. Then came Mizora and a terrible mistake that seems to have ironically implanted both a desire and capacity to be a better man, but at the same time set up a situation such that just as he learns to want that, he'll slowly be dragged into more and more evil either to satisfy her demands or to finally win free of her (typical devil!). Depending on how things go, his deal with Mizora could irredeemably compromise him, getting him stuck in CN or even slipping further into evil, or he could break free and become the person he's pretended to be.
