Judging by the last time a CA issued a CA=yes certificate for MITM, nothing will happen to it. Mozilla will send another "strongly worded letter" [1] and then fail to take any action at all.
"2) Review your CA operations and customers to ensure that there are no certificates chaining up to your trust anchors that are included in Mozilla’s program that may be used for MITM or “traffic management” of domain names or IP addresses that the certificate holder does not own or control. Mozilla’s CA Certificate Enforcement Policy has been updated to make it clear that Mozilla will not tolerate this use of publicly trusted certificates."
[1]: https://wiki.mozilla.org/CA:Communications
"2) Review your CA operations and customers to ensure that there are no certificates chaining up to your trust anchors that are included in Mozilla’s program that may be used for MITM or “traffic management” of domain names or IP addresses that the certificate holder does not own or control. Mozilla’s CA Certificate Enforcement Policy has been updated to make it clear that Mozilla will not tolerate this use of publicly trusted certificates."