It happened.
I lost contact with the wife about 10pm last night after she'd messaged me telling me how well it was going. The next thing I heard from her was a text message at 1am this morning telling me she was on her way home and that she had "done the deed". She said she had fucked him but he hadn't cum inside of her. She told me it was the best sex she had had in a long time (at no offense to me, she said - and of course none was taken) but that it just felt incredible and liberating having another man inside of her. She said she really enjoyed just having sex, no emotion etc.
And she's up for doing it again.