Forgive me if this has been mentioned, I searched around a bit and didn't see it. Anyway, I just noticed that there is a sword design in the background on each of the Part title pages (the pages that show a piece of paper and say "Part 1 Above Silence," etc). The sword on parts 1 and 5 is the symbol of the windrunners which is depressed into the front of the hardcover, what I think I've seen mentioned as the depiction of Jezrien's honorblade. So, whose blades do the other two represent? I kinda think those images would have been put there deliberately, perhaps indicating the future Radiant order of a character in that part.
So, we can match the blades' hilts to the radiant order symbols on the herald/order/surge diagram. The blade on part 2 and 4 looks to me like the right hand side top symbol, Nalan's, although it is kind of hard to tell. The characters listed in both parts are Kaladin, Dalinar, and Adolin. So, perhaps Dalinar or Adolin (or both) will become part of Nalan's order of Radiants. The attributes just and confident certainly fit them in my opinion.
The blade on part 3 looks very similar to the right hand side bottom symbol, Chach's. Shallan and Kaladin are the listed characters for that part, so, Shallan may be in Chach's order. I'd say she's brave, and... maybe obedient. Now, I know that there are theories about Shallan's future order that clash with this, and I'm not sure how to rectify them. But I thought I'd throw this out there anyway.
I'd be surprised if nobody's noticed this before, so if it's been mentioned just disregard and point me towards the old discussion. If somehow it is new info though, let me know what you think :)/>