According to the official brochure of "Kara no Kyoukai 7: Satsujin Kousatsu (Part 2)
", the epilogue chapter of the original novel will be released either as an OVA or a special movie.
The epilogue titled "Kara no Kyoukai
" is about a conversation between Mikiya and 「 」.
Nasu Kinoko said that the chapter is the essential part of the whole series, so ufotable proposed a separate movie instead of adding extra 5min part at the end of the chapter 7.
Source:Scan of the brochure