Nothing saying we can't get new non-focus viewpoints as well, just saying Szeth will get the focus in book 4.
Also, I was reading the other day, and I noticed that in the part where Dalinar saves Bridge 4 from being shot to bits by enraged Parshendi, Kaladin notices that his armour "seemed to glow.". So that's another apparent example of Dalinar's Plate being glowy. Also Syl likes him apparently, which is quite telling. He's almost certainly on the path to Radiantnenss.