Hi
to the comment above.
Before you migrate SEPM from the present one to the old one make sure all your client have the latest policy where the server name is also part of the management server list.
After your have successfully migrated to the new server with a new static IP, your client will communicate to the new server cause it would have the same host name as the old one, once all your clients are communicating, then add the new IP in Manager server list.
Configuring a management server list
http://www.symantec.com/docs/HOWTO55402
Hope this helps.