Lets say it did end.... Where would Saudi get its military equipment from? Russian equipment has been shown the be terrible so the Saudis would want to buy only the best. That leaves them with Western equipment which they can see the results of compared to Russian in Ukraine or possibly Chinese but that equipment isn't battle-proven like the other two.

Saudi oil depends on US missile interceptors and which have shown to be worth every penny... the Patriot system is mostly 80's and 90's technology and is still knocking top-of-the-line missiles outta the sky. Not to mention the US is the largest oil producer and if someone like Trump was elected and he went drill baby drill and flooded the oil markets it would destroy these oil countries' economies.

For Saudi there isn't a lot to gain from wading to far away from the USD if this is the case. I could see the US being okay with them also using the Euro but if they start deciding to use the Yen or Rubble it isn't a intelligent move when the Crown Prince is a hell of a smart guy