These figures would have been respectable (though not outstanding) in the show's earlier heyday, when there were less channels competing. For the current TV market, they're pretty good.
Edit: looks like it'll be the tenth Doctor who returns though, theoretically leaving only three more lives. I'm sure there'll be a way around the limit if it's profitable though. Maybe the Doctor will turn into a gelatinous snake and possess an ambulance driver. Yes, that seems pretty likely.
