Is it possible to define an animation transition between tabs, so that instead of an instantaneous display switch, the tab page does something else, such as flips over to show the new tab, or cross-fades, (or any other transition)?
There is nothing currently in the control that will provide this capability. The xamTabControl, which is a derived TabControl, just has a single ContentPresenter that is used to represent the Content of the Selected TabItem. To facilitate what you are asking it would need to be able to temporarily display both the old and new content. You may submit a feature request for adding this in the future.