I think the issue with the Saudi's is complex
A lot of the support coming from Saudi Arabia is not directly through the government. Rather the Saudis have encouraged an extreme brand of Islam inside their own country. The people who follow that brand then use their resources to provide aid and comfort to AQ, AQAP, ISIL, and whomever else. The government either doesn't want to shut this down, or fears if it tries it will fall victim to internal revolution. Either way, the Saudis are often working at cross purposes. The government often does side with the US (and often not) while the people usually side against the west.
Where we are stuck, if this Saudi government falls what will replace it will be anti-western. But if they want to fund AQAP, and AQAP is stuck fighting Iran in Yemen and not trying to export terror, I see that as good. The problem is that areas of no government seem to allow for rapid growth of terrorist groups. So I'm not certain I want this to drag out, but if it does and Iran wins, it'll be there problem to try and crush these groups.