Answer
PowerVS is IBM Power infrastructure hosted in IBM Cloud, running the same IBM i, AIX, or Linux on Power operating environments and the same Db2 for i engine as an on-premises server. It is an extension of the platform, not a replacement for it.
Migrating off Power means moving a workload to a different architecture entirely, which usually means rewriting or re-platforming the applications running on it. PowerVS avoids that by letting a workload move to the cloud, or simply extend into it for capacity, disaster recovery, or a bounded AI project, while the applications, security configuration, and high availability design carry over unchanged.