Hey there, I had a lil idea about 2 promo pics,
So this is spoiler for season 4, 2 pics for last ep + my theory.
The pic of old Henry , I think that at this moment he sees the ghosts of his wife, that's why he has this expression,

look now the pic of Henry,KOA & Mary (I know it's very tiny, but look at Henry) He's dressed with the same cloths as in pic one,

so thats' my theory for this stunned face.^^ Just wanted to share this idea, what do you think?