Hi,
Thank you for posting in Symantec community.
I would be glad to answer your question.
If you wish to move SEPM from one machine to another with the help of replication, Replication is an option, decide whether to go or not. Because if you do replication and remove the old server that is the Primary SEPM, in future if you want to do replication you will not be able to do so.
This is by design, this is genuine warning message. Do not remove primary server from the network.
Check this article to learn more about replication:
Replication and considerations
https://www-secure.symantec.com/connect/articles/replication-and-considerations