Not surprising at all. To date, the 4th movie has brought in over a billion dollars worldwide. So even if people didn't care for the most recent film, it is still very successful. While I think it's fine at 4 films, Disney recognizes a cash cow when they see one... and I'll still go see any other films they make. As long as Johnny is in it, of course. And he's already said many times he'll continue to be in them as long as they continue to make them.