affy1392,
I am not sure if I understand you but after re-reading, its sound like we won't have any issues. Let me give more details.
Current 5.5 (valid license keys for vCenter/ESXi hosts)
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VS (vcenter)
host1
host2
host5
6.5 (vCenter built today)
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VS1 (has 60 days trial period)
host3 (disconnected from VS vCenter today (has not been removed) and joined into this vCenter today. Had a warning about the license being on both vCenters)
host4 (disconnected from VS vCenter today (has not been removed) and joined into this vCenter today. Had a warning about the license being on both vCenters)
We plan to upgrade host3 & host4 tomorrow to 6.5. If it successful, we will bring in the rest of the hosts from VS vCenter. We are in the process of requesting keys from VMware support (just opened a ticket).
TT.