This may be what Charles Dance was speaking of when he said that we will see more of Tywin Lannister. Up until now, Game of Thrones has been completely devoid of flashback scenes through its first four seasons. That is soon going to change.
David Benioff and Dan Weiss revealed the change during a Q&A with film students in Spain. Here is the roughly translated quote which was not attributed to a particular producer: "By making the first season, we set a rule: No prophecies, dreams or flashbacks. We failed the first two and this season the third. So yes, this season will finally have flashbacks."
Though they said 'flashbacks', as in plural, there is only one known flashback so far and that is currently set to open up season five.