I don’t think there is anything definitive.
I believe Larian initially indicated that they intended to implement PHB classes (or perhaps that was just races?) in which case we could expect Monk, but Artificer isn’t PHB. That said, we do already have race (Githyanki and I think deep gnome) and subclass (Oathbreaker paladin) options that aren’t PHB so there’s some hope that we might get some extra choices at release.
I think it was in an early AMA that it was said multiclassing was intended to be part of the game. I don’t think I’ve seen anything since from Larian, though someone here did mention they thought there might have been more recent reconfirmation.
Personally, I’ll probably start with a Wild Magic Sorceror playthrough, but reserve my right to change my mind! I’ll almost certainly start with a custom character that doesn’t share a class with any available origin characters, though.
