There probably not be any more main races or classes added but I think some more bits will be added through patches...stuff like subraces or subclasses. And while I doubt there will be any big DLC that adds story or major plot I suspect there will probably be something akin to the DOS2 Definitive Edition in time for BG3 with minor DLC like some packs of items and the sorts. But whatever their intentions Larian have never been in the habit of announcing such things far in advance...if Larian plan them they will be announced when they are ready and no sooner.
