Officlally no date for Season 3 yet (from Dan Harmon's mouth)

http://www.indiewire.com/2017/01/rick-and-morty-dan-harmon-season-3-adult-swim-1201772265/

“I’m so sorry,” Harmon told the crowd at YouTube’s pop-up space in Park City, Utah, where he sat down with IndieWire for a chat about his career. “I don’t have a release date for Season 3. It’s not that I know it and I’m not allowed to say it; it’s [Adult Swim’s] domain. What I will tell you is it’s late because of us, it’s late because of me.”

Harmon was brutally honest in taking the blame: “If Justin were here he’d agree. He and I would go, ‘Yeah, we *beep* up,’ and it’s hard to put your finger on how we *beep* up. ‘Rick and Morty’ keeps taking longer and longer to write, and I don’t know why.”