If you do a Get-PowerCLIVersion, you will see that the vCloud Snapin is still 1.5. PowerCLI is supported on vSphere 5.1, therefore the version number was changed to 5.1.
PS>Get-PowerCLIVersion
PowerCLI Version
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VMware vSphere PowerCLI 5.1 Release 1 build 793510
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Snapin Versions
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VMWare AutoDeploy PowerCLI Component 5.1 build 768137
VMWare ImageBuilder PowerCLI Component 5.1 build 768137
VMware vCloud Director PowerCLI Component 1.5 build 793505
VMware License PowerCLI Component 5.1 build 669840
VMware vSphere PowerCLI Component 5.1 build 793489