[larsmak]

I'd say that depends on what kind of service the provider is offering. Later generation cloud providers might specializing in providing such VMs - Heroku and GAE comes to mind. But on providers that offer more "bare metal" VMs one should not expect such migration. Indeed it would be almost impossible to do, since it would require a lot of information about the application you are running. Heroku and GAE solves this by limiting the capabilities of the VMs so that they have more control/information about the running applications.