Well, I'll keep this short. They're probably gonny find some useful material in Equestria (maybe something like in "Avatar", yet again, maybe just pure ol' oil, heck, they'll find SOMETHING). Then they're gonna exploit Equestria. Because come on. Even with all magic in Equestria, you can't stop some good ol' nukes.
PS. I would NOT like this to happen, it's just my prediction