Patch 5.0.4 brought some interesting changes to Pandaria Introduction.
Note that this is by no means the final version and everything is subject to change at any given phase of the development.
In Valley of Honor a Portal has been added. Pandaren can return to Pandaria, once they complete the introduction.
Both Horde and Alliance have an introduction. You start off as neutral, without a faction. Afterwards, you will have to choose either Horde or the Alliance.
The Alliance version has not been implemented yet. Here's the portal leading back to Pandaria.
Horde Pandaria Introduction Video can be viewed below: