All probably part...
... of a bigger story arc.
Remember earlier on last season, people were pointing to what was percieved to be a continuty error early on in the series, when the doctors jacket disappeared, then in the last episode it all made sense, because the jacketless doctor went back into his own timeline and interacted with the characters (or was it he was wearing the jacket when he went back to his jacketless past, i forget now)
Same will hapen with the Big Bang. It was stopped (for now) but we'll still to find out why it happenned.
I also predict we'll find out about the Tardis hidden behind a perception field in that upstairs flat, which seemed to respond to the Doctor, oh and I'm still awaiting an explanation from that Blue Grass episode, why their future selves were stood across the fields waving back.
The Moff seems to be good at little arcs within big arcs, and seems to lay seeds in episodes that in future episodes become "oh now that makes sense" moments. I wouldn't be surprised if we're seeing a 3-4 year arc a'la B5. At the end of it they'll send a space station back in time, to start it all off again :p