I'm not a C4 dealer. My understanding is that configurations are built in the cloud. If this is the case, disabling a dropped dealer would be very easy for C4.

For RTI, the dealer could continue to support a customer for as long as the dealer had a platform that supported currently installed software. Things might become difficult if newly introduced hardware, not supported by the legacy software, was added to the system or if a driver needed an update. A prime example of this situation would be the new Weather driver and the Sonos driver because the system will not continue to work properly with the legacy drivers.