For the Saudis, a Trump Administration is like the proverbial box of chocolates: they just don’t know what they’re getting.
On the one hand, Trump, like Obama but unlike Clinton, has openly expressed doubts about the kingdom’s value as an ally. He has indicated that he would demand large payments from them for protection, and he clearly intends to abandon their Sunni surrogates in Syria. On the other hand, he has also suggested that he plans to renegotiate the Iran nuclear deal, a course of action that could very well lead to a war between the US and the Saudis’ chief nemesis.
Which way will this go? In all likelihood, Trump hasn’t given the issue much thought, so if he doesn’t know, neither does anyone else. My guess is that the outcome will be dictated largely by his choice of advisers. If he surrounds himself with members of the Republican foreign policy establishment, the Saudis will have less reason for concern.