Foster to adopt in PA

Question... if you are fostering a child(ren) and they are in your home for some time and their goal changes to adoption. If there is no family to take the children, do foster parents get "first dibbs" on their foster children, or do they pick several families to interview and pick one? I thought the reason people foster-to-adopt was because they'd get first dibbs on their foster children if they were up for adoption.