Lots of spoiler speculation:
spoiler (click to show/hide)
So, how about Rose Tyler on the TARDIS viewscreen? In addition to that, it seems like the entire season is building up until she boards the TARDIS again. Hopefully Rose isn't the mother. That wouldn't be too credible IMO.
Actually:
spoiler (click to show/hide)
Jenny (the titular character) tells The Doctor that she saw someone called Susan die in the Time War, which upsets him greatly.
Everyone that's seen the episode so far has ranked it the worst of the season, though, with the most frequent complaint being that it tries to cram too much into one episode and comes out muddled. One of the other spoilers is:
spoiler (click to show/hide)
The Doctor doesn't need a female to spawn a daughter - he is capable of doing it all on his own.