The xfce4 drop-down functionality was recently added in Xfce4-terminal version 0.6.1. whose release was announced just about two weeks ago.
According to launchpad, there appear to only be source packages(not .deb files) for the Raring release.
Adding the PPA:
There are PPAs available from the xfce-dev team for 12.04 and 12.10.
To add these repositories, run the following commands from the terminal Ctrl-Alt-t:
sudo add-apt-repository ppa:xubuntu-dev/xfce-4.12
sudo apt-get update
sudo apt-get install xfce4-terminal
Configuring the keyboard shortcut:
In order to set up the Super-Space functionality, follow these steps:
- Go to Applications Menu --> Settings --> Keyboard.
- Select the Application Shortcuts Tab and Select the Add button.
- For the shortcut command field, enter
xfce4-terminal --drop-down and select OK.
- Finally, enter the keyboard combination that you wish to use for your shortcut.
For more information on this functionality, see the webupd8 article or this one article. The webupd8 article has instructions on configuring the drop-down functionality that you are looking for, I believe.