I'd have to disagree with this assumption. I don't think Cobb would STILL be wearing his wedding ring in any dream, BECAUSE. When they were in limbo. He finally came to terms with his guilt and he realized that they already had spent their time together. "In my dreams, we're still together..." this is one of his lines.. But... He already let her go in his dreams!! So it would make sense that you'd never see his ring again!