I would say that with Reed in the rotation that we are going to need less rotation. She is a true, post up player from what I saw today and she is going to log a lot of minutes. I think that Gayle will come in to give Reed a blow but that Reed will get the majority of the minutes. If Earnie does return, she can also play the 5 if needed. A rotation of Reed, Gayle and Kristen sounds fairly solid to me and to me will make us even stronger in the post than we were this year. I have a feeling that Gayle is going to come back with a pretty effective offensive game next year.
And you are right, Cook seldom played, so replacing her does not seem a big issue to me.
Of course, who couldn't stand to have another player like Bone in the rotation.