Google this:
Walsh, Declan (December 5, 2010). "WikiLeaks cables portray Saudi Arabia as a cash machine for terrorists". The Guardian (London).
"US embassy cables: Hillary Clinton says Saudi Arabia 'a critical source of terrorist funding'". The Guardian (London). December 5, 2010.
Fact remains, the Saudis are not a threat to provide WMD to the terrorists.
Separately, I would assume the Saudis are in conflict with the Caliphate movement. As the Guardians of Mecca and Medina, the Saudis probably aren't interested in a competing group trying to establish a Caliphate. This seems like a schism that could be exploited...