Though there has yet to be an announcement from developer Obsidian Entertainment or publisher THQ, the upcoming role-playing game set in the South Park continuity appears to have a name, according to an early listing on the Xbox Live Marketplace. It's "The Stick of Truth".
You can see its provisional cover art at the link on Xbox Live. That release date (today) is quite erroneous.
Rumour: Obsidian's South Park RPG Has A New Name [Game Informer]