Possibly only with mods (are mods confirmed btw?), but currently it appears to early to tell. The Portraits so far seen are of the 3d rendered characters and are themselves 3d? I am assuming depending on how deep chracter customisation goes, this is done so that the portrait matches the character model.
I have to say I do have a soft spot for the painted portraits of the previous titles though and even if those assets couldn't be used, I just like the art style of the painted pics.
