I realise this might sound a bit cruel to some, but part of me hopes that if they had filmed any Series 5 episodes, they don't show them. It would just be too painful to watch, knowing she died so shortly after.
My guess is that they will add the six episodes / three stories to the upcoming fourth season dvd release (which will come out, what, November?). But I think this is the end of the series.
I can only recall one other time when there was an active series running, named for the title character, that continued after the death of that character (Valerie, which eventually became "The Hogan Family") but even then, the actress was still with us. This is new territory.