Yeah, there's never been a TF rooster. There should be. But any birdformer would do. Makes sense than say yet another Optimus Prime or other G1 character who bears absolutely no relevance to the Zodiac animal.
But isn't that what they're doing now? First they had the Year of the Dragon Optimus Prime, now the Year of the Snake Optimus Prime and Omega Supreme, now the Year of the Horse toys for next year... but the way they're doing it just seems to be, "Grab a random big expensive toy and slap it with a repaint and exclusive box." Care factor zilch, except for Omega Supreme only because he's an approximation of WFC Omega Supreme.