Ok so i think i have seen the season 4 trailer about 27 times and there is one little girl in the trailer with carol in 2 scenes.

In one scene she is seen in carol's knife club and in a another scene she is scene with carol entering a room.

I dont know why but i think she will replace sophia, she looks about 11 years old and appears to have a bond with carol.
Season 4 survivor (3)