If you leave it as it is it appears to be an exposure mistake and you can't add light to the dark areas without sapping a massive amount of quality. Thus the only choice is to darken the photo to make is silhouette. However by doing so you've introduced not only a large black area of dead space to the base of the shot, but also pushed attention to the relationship between the two small people and the big sky areas; and personally I just don't see an association/link between them. The clouds appear as random and don't really make a suitable frame for the couple (which would need to be cropped closer I suspect any way).
In the end I think its one to learn from and to put into the duff shots list.
EDIT - also we traditionally associate silhouette with the beginning or end of the day, when light is more sparse; however the light in this in the sky appears to be middle of the day, which conflicts in the average persons mind with the black/dark presentation of the main subject (makes it look more like a sky has been imposed over an original photo).