We will be pushing a Zuora for Salesforce maintenance release (Quotes 9.20) to all 9.19+ Sandbox orgs after 6 pm Pacific on December 19th, 2019.
The push upgrade to all 9.19+ Production orgs will be scheduled for after 6 pm Pacific on January 7th, 2020.
This upgrade will be deployed to orgs on Quotes version 9.19, 9.19.1 and 9.19.2, and is inclusive of changes in Quotes 9.19.1 and 9.19.2. Quotes 9.20 will include minor fixes. Release Notes will be available soon with details.