Linux Mint Debian (LMDE) is a rolling release distribution based on Debian Testing.
LMDE Update Pack 4, which will include Linux Kernel 3.2, Mate Desktop 1.2 (a renamed GNOME 2 desktop), Cinnamon 1.4 (GNOME Shell fork), GNOME Shell 3.2.2, KDE 4.7.4 and Xfce 4.8, "is being prepared and tested at the moment" and should be available soon.
In a comment, Clement Lefebvre, the Linux Mint Project Leader, has specified that a new respin of LMDE ISOs will be available too when Update Pack 4 will be released. He also stated that it hasn't been decided yet if MATE or Cinnamon will be made default and if they will both be on the ISO, but "both will be fully supported".
If you don't like any of the desktop environments available with LMDE Update Pack 4, you'll be able to avoid the update, keeping GNOME 2, by changing the software sources as explained on the Linux Mint blog.
Install Linux Mint Debian Update Pack 4 (testing only!)
LMDE Update Pack 4 can already be tested: download LMDE from HERE, then install Update Pack 3 using the Update Manager and then, to install Update Pack 4, you'll need to add the Linux Mint Debian testing repositories - to do this, run the following command in a terminal:
gksu gedit /etc/apt/sources.list
And replace the contents of this file with the following repositories:
deb http://packages.linuxmint.com/ debian main upstream import deb http://debian.linuxmint.com/incoming testing main contrib non-free deb http://debian.linuxmint.com/incoming/security testing/updates main contrib non-free deb http://debian.linuxmint.com/incoming/multimedia testing main non-free
Then open the Linux Mint Update Manager, click "Refresh" so the software sources are updated and LMDE Update Pack 4 should be available for installation.
After the upgrade, only the GNOME Shell and GNOME Fallback sessions will be available:
|LMDE - GNOME Shell|
To install Cinnamon, use the following command:
sudo apt-get install cinnamon
To install MATE, use:
sudo apt-get install mate-desktop-environment
Then log out and select MATE / Cinnamon from the GDM login screen.
via Linux Mint blog