As of February 1st, HMH says Saxon Homeschool Kits have not been discontinued.

After Saxon Publishers was sold to Houghton Mifflin Harcourt, it became clear they did not understand nor support John Saxon's unique teaching methods. We knew it would only be a matter of time before they changed and/or stopped publishing Saxon books. That is one of the main reasons we created Shormann Math.

For Pre-Algebra - Calculus, this new updated version of DIVE + Saxon Math is based on John Saxon's original teaching methods but updated with 21st Century concepts and teaches all the concepts required to excel on the new PSAT & SAT that are not taught in Saxon. Shormann Math offers daily video lessons from a biblical foundation, interactive assignments with auto-grading, video solutions, and Q&A support with Dr. Shormann. It also has an eTextbook, eSolutions Manual, and an eTextbook so it can be completed off-line. Learn More: Shormann Math