No, the Veeam MP will not lose historical data, even if you upgrade from v6.5 to v8.0, or even reinstall.
All the objects (Hosts, VMs etc) will be rediscovered with the same ID. We control the object ID during discovery, and use our own unique (but consistent) ID. (e.g. Host FQDN)
And the MP class model has not changed between 6.5 and 8.0. Therefore all reports and charts will be continuous.(except for a small gap during (re)discovery while the upgraded Collectors initialise)
And you will find that using Management Servers for Veeam Collectors gives you much better performance and scalability. This is why we made the decision to use this as default option.
Hope that helps - any other questions on the upgrade, please let us know!
Vice President, Product Management