The New Jersey 1915 State Census is listed under current projects on Familysearch's indexing page.
But apparently it is not ready yet to be indexed. I will keep you updated. If I had to guess portions will be indexed and no images will be available.
About This Project (from familysearch)
State censuses were taken in New Jersey every ten years, between the
dates of the federal census, from 1855 until 1915. This project is to
create an index for the 1915 state census. The census contains
information about families and individuals residing in New Jersey on
June 1, 1915. In addition to standard census information, such as the
names and genders of individuals in family groups, this census also
included the month and year of birth, along with the age of each person
recorded in the census. This records collection includes all counties
and is organized by county.
Ed