How will plank handle multiple windows of an application?

In docky 2.x multiple windows of an application are accessed by right clicking and choosing between the window titles that pop up. If the user just clicks on the icon, all the windows are either hidden or shown.
Dockbarx has a somewhat more user-friendly style of displaying previews of each window.
Unity's Launcher activates a compiz scale (i think) which presents all the windows on the screen together to allow the user to pick.

What system will Plank use?