Update (May 4, 1:28pm EST): A representative from Sega of America issued the following statement:
As most recently announced during SXSW, Sonic Mania is scheduled to be released this Summer 2017. We have not released a specific date beyond this timeframe. We look forward to officially announcing the date in the near future.
A live shot of the website at the time of this writing indicates that all four collectors editions will release on the 22nd. Amazon still has their release date set for Thursday, August 31st, where the final day of a month is usually a placeholder date. Nintendo’s website, as well as PSN and Xbox Live all have the game listed for a Summer 2017 release.
We have reached out to our contacts at Sega of America for a response and will update this article with a response, should one become available.