Speaking with www.thedailybeast.com, the head writer of Doctor Who shared a few facts and added a bit of speculation about the future of the series. Speaking about the inception of River Song and how her character came into being, Moffat revealed:
“I thought… What if one of the archaeologists knows him, but he doesn’t know the archaeologist?.. What if it’s a woman who flirts with him in a rather proprietary way? Then a whole story explodes in your head…”
For all of you that were wondering “just how long has the idea been kicking around that she is Amy and Rory’s daughter?” the writer commented:
“When I introduced Amy Pond, it was with the possibility that this could be the mother of River, and that’s why I put the “Pond” in…”
So it’s an idea that’s been around since Moffat took over!