Hi DH,
Yes. I believe when you execute the "install firmware" command, it will check if the BootROM version on any other IO module, MSM, etc.. need updating as well, and will let you know if that is the case. You have the option to select/specify which one(s) you would like to update. As you know updating the BootROM on Slot 4 will require a reboot of the module. You can use the "disable slot 4", "enable slot 4" to reboot the I/O module in question.
Please let us know if you have any other questions.
Thank you.
Best regards,
Andrew