CAPI (v1) is now a very old protocol that is no longer used. The deprecation effort will take place in the 7.0 vehicle.
For deprecation, and to minimize breakage, there will be no changes to XDCR's REST endpoint and behavior regarding CAPI. This means that XDCR will still allow replication to be created with CAPI specified, or for existing replication to be modified to have either CAPI or XMEM as its replication type. This also means the default replication setting can be set as either CAPI or XMEM.
However, any replication (new or existing) that uses CAPI will fail to start and then automatically paused. This means that a replication pipeline creation, if using CAPI, will fail with an error, and not retry to restart.
To recover from this, users should directly use the XDCR REST Endpoint to change the replication type from capi to xmem.
Note that if user's default replication setting uses CAPI by default, they should ensure that the default replication setting uses XMEM.