Since I've only recently returned and hardly done anything I'll keep playing until we know. I very highly doubt I'll stick around if they give a definitive no, even if I haven't played a char of each of the base classes going both light and dark side (yes, I tend to play all possible variants, one thing I like about Rift is that with its Role system one char can be multiple variants, and they allow a lot of variance for their four base classes). Although, I did create a Jedi Consular that I then ran up to lvl 10 to see the Sage and Shadow skill trees (she was going to go Sage from the get-go, due to the archetype I was using for her, but I wanted the comparison), and sadly it looks to me like on the force using classes they just did a copy-paste-and-edit as you have skill in the exact same spots on the skill trees with the exact same effects. I think the only actual difference between the Sorcerer and the Sage is the effects of the skill the Sage gets in place of Chain Lightning and some of its enhancement skills. Oh, and with the Sith doing Energy damage while the Jedi does Kinetic damage, but the damage values are the same so that doesn't mean anything unless you have both fighting together against enemies with mixed weaknesses/strengths.
It plays a bit differently in other areas, like stun vs knockback. But yeah, that's why my JK is Sentinel and going Juggernaut with my SW, IA is OP while Smuggler is Gunslinger. However, I love BH Arsenal Spec so much, I'm just repeating it's Trooper variant