My take has been for some time now that the duck pond is already explained, just indirectly. I used the duck pond to correctly predict how the Doctor would be brought back at the end of season five, at least, so it feels valid in my mind.

The question was, how is it a duck pond if it hasn't got any ducks in it? The answer, as I see it, is that it's a duck pond because people remember the ducks. If they didn't, it would just be a pond.

That's how Amy brings the Doctor back at the end. She remembers him. I see it as a thematic sort of link.

But then, there are also people who simply believe that the crack in Amy's house was swallowing things around town as well, and swallowed the ducks. That doesn't seem to be a very important point though. What does it really matter if the crack was swallowing other things? The Doctor seemed to think the question was important, and repeats it later in the second Weeping Angels episode. Unless it's just supposed to suggest the fact that the crack ate Amy's family as well.

But either way, I'm really looking forward to the finale. Now that we've seen River's beginning and her end, I'm wondering if this might be the end of her on the show. Once we get the nature of her relationship with the Doctor solved, I wouldn't be surprised if they chose to leave the rest of their story offscreen. We've already seen a lot of offscreen stuff between the two of them (picnic at Asgard, Easter Island, whatever she mentioned at the start of A Good Man Goes To War, etc). Since they keep meeting in the wrong order, there's no real way for them to have sustained adventures. They always have to part ways at the end of the day. If we get answers about her, I think they might just let the rest of their adventures take place offscreen.

If not, then we're in for a Riverful season next year, because Kingston and Smith aren't going to be around forever. I think I would prefer if the series went on as usual and River's character gets left between the pages once we get our answers.