It was literally never confirmed that super skinny humans would be playable, so I wouldn’t count on it. The big humans are the humans with Drust heritage - the thin ones and the muscular (normal) ones are just regular people.
So, realistically, lore-wise, only the big humans can be Druids (and, I’d wager, Shaman) by nature. Meaning super skinny and regular humans don’t really fit the bill for the more unique class options for the new humans.
I wouldn’t count on them ever becoming a playable option.