Prediction: he retired now so that the book, (which he has been secretly writing with his Dem handlers), can be released before the election. He will follow the Bolton pattern; submit it for review then publish it after a denial from the review folks. Causing a media storm over the denial, court case and then claim the book has already been release so nothing the govt can do to stop it.
You may be right, but he is still subject to recall to active duty so he does not have the same ability as Bolton in that regard.