In this interview with GameFocus, Rare's Justin Cook has confirmed that Viva Piñata: Trouble in Paradise will, definitely, have proper online multiplay.
"We have a new two-player mode where you can share a garden with the person sitting next to you on the sofa," said Cook. "I can confirm that there will be multiplayer over Live this time."
This will have the faithful squealing with delight. There's plenty more through the link.