UPDATE: According to DoC, in addition to the changes posted below, cardholders now also have to wait 24 months from getting the signup bonus on a Sapphire product before getting another signup bonus on an additional Sapphire product. This clock starts once the bonus is issued.
Additionally, there will be no changes to current cardholders with multiple Sapphire products.
According to multiple data points on r/churning, Chase has implemented a new rule where applications for a new Sapphire product will be auto-declined if the cardholder currently holds any other Sapphire product. This means if you currently hold the Chase Sapphire Reserve (CSR), Chase Sapphire Preferred (CSP), or no-annual fee Chase Sapphire and apply for any of the other Sapphire products, you will be declined. According to Chase customer-service representatives, this rule was implemented on August 27, 2017 and there is no way to bypass this.
There are no data points yet regarding how this impacts product changes, or if in-branch pre-approvals may bypass this rule similar to the 5/24 rule. If anyone attempts to product change to one of the Sapphire products while already holding another Sapphire product, please let us know what happens.