we have recently proved that we can cross site vmotion between 2 data centers and in this case the vsphere has to be the same versions along with some other requirements
but now I would like to be able to vmotion from one vcenter on Vsphere 6.0 to a vcenter in the same datacenter on Vsphere 6.5 is this possible ? or maybe to ask the question a different way how to get my production VM's that I want to move over to the other datacenter into the Vsphere 6.5 vcenter without shutting down the VM's when they are in the 6.0 Vsphere Vcenter
It's part of it, yes, but there are other considerations. You need the proper license, you need the correct versions, you need the correct type of switches at source and destination, and you need vMotion compatibility and connectivity. So it's not just one or even two things that must align.