I can't see why the Suns would want Dunn. They've currently got Bledsoe, Knight and Booker and trading Knight for Dunn doesn't balance out their team, it still gives them two starting quality PGs and a young and very promising SG.
I think if the Suns were to trade Bledsoe or Knight they'd do something more like what the Warriors did with Ellis and move one of their guards in an effort to balance the roster, create clear roles for their guards etc. And I think the Suns are looking at what Portland did this year and thinking that they can ret00l around a high scoring backcourt and get better in a hurry. I don't really agree but there's a blueprint there that is pretty easy to follow.
And honestly, I don't see the value for the Kings either. I'm not convinced that Knight is significantly better than Collison and he'd eat up $10 million more of the caproom than the #8 pick would. Knight shot more often but had lower percentages than DC and the Suns were one of the worst defensive teams in the league and were worse defensively (by a few points per 100 possessions) with him on the floor.