I think Herbie and his manager did the right thing by holding off contract negotiations for the first month of the season. Backing Herbie to improve his form. Which he did.
Herbie's value has rocketed. He's been one of the top five players at the club over the last month. Which, at his current price, makes him something of a bargain. We should enjoy that while it lasts.
Regardless of whether Herbie wants to stay or the Broncos want to keep him, we can't really afford to pay his street value now. We already have an expensive centre. It's dubious moneyball to splash out on two. Not with Deine Mariner on his way up, and Brenko standing by to warm his seat. Both contracted next season.
So Wayne gets to win in two ways: he nabs a strike centre who's not only at the top of his game but potentially on the rise, and he gets to kick the Broncos right in the nuts. Herbie wins by getting a pay bump, and playing on his preferred side of the field. He has to leave if Wayne offers him more money. We have to let him go, and wish him well.
In short, even if we have the cash to retain Herbie it doesn't seem like the right place to spend it. I think he's gone.