Televi-kun had revealed the cover of Kamen Rider Zero-One Chozenshu Hiden Box yesterday in their Twitter. The cover revealed the list of topics that will be covered in it.
In this list they had mentioned that they are going to focus on "Zero-One Others: Kamen Rider MetsubouJinrai". This sounds like the title of Kamen Rider Zero-One's V-Cinext Spin-off that will focus on MetsubouJinrai.
This tweet was later deleted maybe because they accidentally revealed the information before the actual announcement.