Power CMS Was replaced by Power CMS Builder in Design Extender.
There really isn't much different between power CMS 2.0.1 and Power CMS Builder in design extender, except for the license.
The Power CMS Solution is licensed for a single domain, Power CMS Builder in Design Extender does not have the same restriction.
There is not much need to update an existing site to Power CMS Builder, but you could certainly use it for other sites you develop.