This is supposedly the cover art, it was announced in a tweet by twi4 today.
— ツイ４ (@twi_yon) 14 de diciembre de 2017
It was also announced that starting tomorrow (today for us) and until January 2nd, the manga will enter hiatus in order to conclude work related to the release of the volume. This means, all the extra content that has to be included in the tankoubon as announced in the cover art.
The volume will be released on January 11th, here’s the link to amazon.
If it is within your means please consider purchasing the volume.