Currently in its 16th edition, The Chicago Manual of Style remains the most comprehensive general authority on editorial style and publishing practices. Answers to questions not addressed in this handbook may be found there. (§3.3)
The reference to CMS’s “current” edition raises the possibility that a new CMS edition may occasion a change in the CMS edition best followed by users of SBLHS2. In addition, on noting the release of CMS17, SBL Press commented that
based on the Chicago Manual of Style, this new edition will no doubt prompt changes to our own style. We will announce relevant changes on this blog in the coming months.
This comment made it sound like changes might be affected in SBL style before the release of SBLHS3 simply based on the release of CMS17. On reaching out to the ever-helpful folks at SBL Press, they’ve confirmed that
Our deference to CMS in matters not explicitly covered in SBLHS2 or on the SBLHS2 blog automatically upgrades to the most current version of CMS. Thus, as of September 1, 2017, we now defer to CMS 17th ed.