It's not that it's wrong to wait and see what happens. I just felt like since he finally admitted the A (after lying about it for so long) that maybe he was ready to work on the marriage. Why else would he finally admit it? Guilt? Did OW dump him?
I think it's quite likely that it's one of those two things, or even a combination of them. At some point, a wayward will want to try to "normalize" their affair into their life as much as possible.