A. Skynet learns about scientific teleportation and creates a portal that will let their troups move in the blink of an eye or B. Find someone who can do magic in a place that has shown no inclination about magic?
If people here could do magic, rest assured that either a) someone would know already or b) they are so good at hiding that no one will ever find them.
I think we're all more afraid of magic, because we don't understand it, but the tech can do so much more damage at this point, because tech is something skynet can achieve easily.