2 cents:
i personally think Karina is gonna be the one that's promoted like Irene/Krystal/Yoona
Winter is gonna be promoted like Seulgi/Taemin
as for the actual post, I think right now, Wonyoung is really the only IT girl right now in Korea. Although, Miyeon is actually gaining traction now on community sites, tbh. Yeji is incredibly popular, and Soyeon, well, she's popular and she's Soyeon, but there's a reason why I don't consider the latter two as IT Girl material.
I think IT Girls are those who sell brands well, most particularly fashion and make-up. They pioneer a fashion trend in their nation. I don't see Soyeon and Yeji doing that- whereas, in their fellow group members, I could see Miyeon and Yuna/Ryujin doing something like that.