Sporting is vastly superior to all the other teams. They have won every game played so far except for a draw against Famalicao. I really think they will stay on the podium until the end, and as for the first position, I really suppose they will keep that as well.
I somehow agree with you but Portuguese league is an inconsistent winning league, a club might be doing well but will suddenly start loosing even to the least clubs, Benfica on the other hand will compete with CP as the league is just starting with 11 matches played so far. Let's see how it goes at season ending.