IIt also depends on what you say next. You can say the "next couple is Mr and Mrs Smith" but I'd say ARE if I was (were?) saying the next couple are wearing a white dress and a dark blue suit
Assuming as ff does that the sentence is to continue with the names of the two individuals, consider this:
Turning the sentence around a bit, would you say "Jack and Jill are the next couple" or "Jack and Jill is the next couple" ?
I would definitely say ARE in both cases because they are in effect the same issue. The device of rearranging what gives rise to uncertainty is often helpful.