Doctor Who- Face of Boe's last message?

What did he mean "You are not alone"? Are there more time lords, or
something from the planet? Or does he just mean the Daleks, because,
if so, that's lame. We already *know* about the Daleks. Or does he not
even mean from the planet?
The wiki page confuses me, probably because I never saw the old
series...

WHY DOES NO ONE GIVE SPOILERS WHEN ASKED FOR?!?!