Spreading predictions about the December premiere of "Rick and Morty" Season 3 has never been justified or confirmed by Adult Swim, and it is highly unlikely to happen based on fan reviews and comments. However, this coming March 2017 might be it as speculations connect with the last episode.
In "Rick and Morty" Season 2 Mr. Poopy Butthole appeared at the end of the last episode saying "What would happen to every character? It will be another year and a half before we find out." The last episode of "Rick and Morty" Season 2 originally aired on the 4th of October 2015; basing on what Mr. Poopy Butthole said starting October 2015 until March 2017 will be a total of 18 months and might justify what Mr. Poopy Butthole have said.
As for the December premiere of "Rick and Morty" Season 3 this just might not happen according to Game N Guide. It was just a result of expectations from the announcement of "Rick and Morty "Season 3 writers that have finished writing the episodes. So far it's already December and still no official announcements are coming from Adult Swim, resulting the "Rick and Morty" Season 3 predictions for this December unlikely to happen.
Further reports regarding the December premiere from News Everyday stating that fans are very much disappointed that the release will not happen this year's last month. Further announcements were made for the 2016's pilot episode and is expected to be released next year, in addition to this Mike Mahan who is another writer of the "Rick and Morty" Season 3 says, the upcoming season is worth the wait.
"Rick and Morty" has been anticipated by fans for its premier this December but most statements from writers don't justify a release for the said month. Let us stick to what Mr. Poopy Butthole said on the last episode of "Rick and Morty" Season 2 "it will be another year and a half before we find out." Subscribe for further updates of "Rick and Morty" Season 3!