But ... let decide the players, I would like it with optional 6. Even without extra modding there were already old screenshots of a very old stage of baldurs gate 3 showing 5 player portraits. Hah!
While our party will consist of 4 people it seems there will be possibility for more units to temporary join our team. There are summons, pets, familiars but also temporary quest companions, if I understood Larian correctly. So it's possible we will have 5 or more characters in our party in certain situations.