As I understand it the tier type only considers your state at the time of purchase, this is from the Fab EULA:
You are only eligible for a Personal - Reference Only tier or Personal tier if, at the time of the Transaction you, together with any controlling entity and other entities under common control with you, have not generated more than $100,000 USD in gross revenue from your commercial activity in the digital content industry in the last 12 months.
Would welcome further clarification from UE/Fab but to me this reads that you would not need to upgrade the licences retroactively?