It appears that howtheduck is right to assume that John's night out will depict him giving into his throbbing biological urges.
Panel 1: We're at the dentist's office and Jean says "So, you're going out on the town with Ted, are you?"
Panel 2: As he points out that while the cat's away, the mice will play, he makes that stupid palms-out gesture Lynn likes to draw.
Panel 3: He then asks what's wrong with a night out. Jean's answer: "Nothing..."
Panel 4: Expect, of course, that when the cat's away, mice tend to turn into rats.
Summary: In the old order, John's evening out led nowhere because he'd rather look, imagine what could have been, realize he had it good and irritate Elly with a smile she never understood. In the new world, we could actually see John break a commandment or two. What really bothers me is that his timing is off; as howtheduck said, when the cat's away, the mouse invites his friends over to watch the playoffs and play poker instead of going barhopping.
