Migration results in a change of IP addresses. The involved process however, should not lead to any connectivity or downtime issues. Traffic will be routed from your old server to your new server once data syncing is complete, and at this stage, you will get the new IPs for creating name servers.
Important: Your name servers will be updated automatically if your domains are registered with us. On successful updation of the DNS, traffic will stop flowing via the old server and it will be taken offline.