GRRM has written episode 4.02, so that might be the PW. A major character death two episodes into the season would be pretty awesome.
Episode 9 will either be the battle at the wall or Oberyn vs. The Mountain. Tyrion killing Tywin will most likely conclude the season.
What interests me the most is how they'll handle Bran's story. he will meet Sam next week, so they have already covered all
of Bran's chapters in ASoS. Which leaves them with three(?) more Bran chapters from book five
to fill 2-3 seasons with. I have absolutely no idea how they are going to pull that off.