I wonder if Ambrose’s and Richie’s visions are connected somehow. Though Santanico wasn’t Santanico yet, in From Dusk Till Dawn 3, Ambrose’s visions could have been from her mother. That is assuming Richie’s visions are from Santanico, which I’m pretty sure they are.
Ambrose does get turned at the end just like Richie did so they may have similar purposes. And he may show up in the series since Carlos did mention Pancho Villa.