Peter Vesterbacka, the "Mighty Eagle" at Rovio just announced during their GDC panel that Angry Birds St. Patricks Day is coming soon as part of Angry Birds Seasons. Does that mean we can expect drunken birds? They're already angry, after all. Little flingable leprechaun birds would as happy as well. Expect it sometime "Well before St. Patrick's Day."
They also spoke briefly about the Angry Birds Rio game, meant to tie-in with the upcoming animated film. "We could make it work nicely with Angry Birds and the backstory. It could be the first time the birds leave the island, and are kidnapped by smugglers. This is not one of these lame movie games, but a separate game that works nicely with teh movie."
Angry Birds Rio is due out on March 22, and will retail for $.99 on Apple's App Store.