Moved to ePO for better handling.
You should be fine. I've reassigned IP addresses on endpoints as well as servers, (infact as a matter of course we build endpoints on one vLAN and then deploy on another, with different IP addresses on each) and all are still able to talk to ePO afterwards.
So long as you dont change the ePO server's IP, they agent will still be able to report in with the new details after the change.
Yes, changing IP addresses of managed systems is fine. All the Agent communication with the ePO server is keyed on the AgentGUID which is assigned at the point the Agent is installed.
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Certified McAfee Product Specialist - ePO