I'm actually kind of glad Dalinar's book is number five. It gives us three more books worth of set-up for him.
Considering that he effectively removed himself from a fighting position at the end of book one, it makes sense that over the course of the next three, he'll take a more administrative role. Although hopefully that will involve some Highprince head-bashing.
But then, after seeing Dalinar as he is now, we'll get flashbacks to the reunification of Alethkar. We'll get to see the Blackthorn in action! And not only that, but we'll see the changes in his way of thinking. This will be a most interesting contrast, I think.
Don't get me wrong, I love Kaladin. But he's only twenty in WoK. He's a young man, and his flashbacks show us the loss of his innocence, basically. I feel like it'd be much the same for Shallan.
I'm very much looking forward to Szeth's backstory. Like, a lot. He's the most mysterious POV character we've met so far.
(Please forgive typos, I'm on my phone :\)