I just saw the formatting up with a blank image and that "Also available in the Five French Films of Luis Bunuel," however the link just went to an error for a nonexistent link It was up for about six hours and then taken down. The formatting appeared next to the ones they've already released (Diary of a Chambermaid, The Milky Way, The Discreet Charm of the Bourgeoisie, The Phantom of Liberty, That Obscure Object of Desire) so I assume it will just be a Criterion re-release with single packaging, although I hope there are even more special features and new artwork. Personally I'm not a huge fan of two or three of those films but for a reasonable price I would consider picking it up. I'll post something in here if it materializes.
My personal conspiracy theory is that this will pave the way for The Four Mexican Films of Luis Bunuel plus Tristana. Janus owns the distribution rights for Tristana, Simon of the Desert, and The Exterminating Angel at a minimum and there are rumours that they also have the rights to El and The Criminal Life of Archibaldo de la Cruz. It's only a matter of time before the first three show up and it would be appropriate to bring out two big Bunuel boxes within the same timeframe.