User blog comment:Rod12/What New Characters would you like to see in Series 5/@comment-4832945-20120101061206/@comment-4650675-20120103110045

I think that, if we're going for series 6 and series 5 isn't the last one, then a two-parter showing the past could be done. What I'm thinking of is, we're left with a major cliffhanger at the end of series 5, even bigger than the one of series 4, and in order to explain what happened, the writers will take us to the past in order to explain the cliffhanger.