Like others have said, I agree that the Third ideal will not come out of the battle with Szeth, and that the Third Ideal will be somehow relating to leadership of some sort. I am going to go out on a limb, however, and say that Kaladin will likely get his 4th or 5th ideal during the battle with Szeth.
If you think about it, Kaladin really got two ideals out of the first book, so it only stands to reason he might get more than one out of this book. I think there is so much that BS wants to get to in the books that the Ideal thing won't be dragged out too much longer, so the others books can focus on other parts of the plot.
I think the 4th will be relating to forgiveness in some way, and the 5th will be related to honor. Just my 2 cents.