As long as your support is valid you should be able to simply upgrade to the latest version. You can validate this easily by visiting the licensing support page, http://www.vmware.com/support/contacts/?src=WWW_ChatChicklet_SupportLicensing.
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no, use the same license keys. Only time you have to change is if you go from say Enterprise to Enterprise Plus. Otherwise the keys are for 4.x
Thanks, thats what I want to hear.