It seems that the action icon now appears when you mouseover the target
frame of a NPC. It doesn't look like it's implemented yet but we can
assume that in the future, we will be able to left click the frame of
the NPC instead of his model to prevent all the issues caused by
players blocking NPCs.
Im guessing this means you will be able to open the dialog window for the NPC just by targeting him. No need to keep scrolling through windows to accept and turn in quests? Same with flightpoints, bombing quests ect..

Maybe they will add some macro command that will allow you to put this to better use