“And I’d give it all away, just to have somewhere to go to ”

Hey I was an early 2000’s kid, and everyone I knew listened to Linkin Park. I can’ talk about Hybrid Exchange without talking about the best band ever.
Microsoft Exchange is a system that is aware that eventually it is going to be in a hybrid state. I often refer to this state as broken. From the second you move the first mailbox in Exchange, you are in a hybrid state. You can also, in some ways, think of this as a broken state.
To figure out what the current set up for your environment, take a look at the Get Hybrid Configuration.
Get-HybridConfiguration
One of the challenges with explaining this to upper leadership, is by nature when you tell someone in IT leadership that you are going to be a broken state for an extended period of time, they have a way of breaking out. I can’t blame them, I would freak out too. The thing to keep in mind is that this is a natural progression of Exchange. There really is no thing as an in place upgrade.