You left out the last part of my post...I said I expect the Texans will treat him as the Colts did Manning.
I don't expect he will leave. But by the same token it's not an impossibility. Improbable yes.
I suspect if they have to keep Carr at the expense of others they will.
I really don't keep up very much with players in free agency or trades. So I can't answer when the last QB to leave was. I don't have any idea.