The comforting words of a few oddball tumblr users who claim to have seen this mystical poster in a manga store (interestingly there have been no other accounts from Japan that corroborate this tale with eye witness accounts of the poster being seen in other stores) doesn't substantiate anything. There's no other witnesses, no advertisements, and no official confirmations of any such content being released.
It just sounds to me like we're riding on the back of a bird without the wings to keep itself afloat.
Oh... sorry. I didn't read your post correctly. I though we were talking about reliable sources for upcoming movie spoilers
About the poster. We'll find out soon.