Using Power CLI/vim-cmd to upgrade VM version of virtual machine

vim-cmd vmsvc/getallvms
vim-cmd vmsvc/upgradM-ID] vmx-[e [VHW-VERSION]

PowerCLI:
$vm=Get-VM -Name VM-NAME
$vm.Version

Set-Vm -VM (Get-VM -Name [VM-NAME]) -Version v[HW-VERSION]

Ref:
http://www.virtuallyghetto.com/2013/10/quick-tip-using-cli-to-upgrade-to.html