The timing and message from the president gave me pause to think that he has framed this as a Sunni problem that crosses states in the region.
I can imagine him going to the Saudis and saying, look, you bastards owe us -- the 9/11 people, OBL, the Islamic State people are all from you guys. Get on the right side of this ISIL thing.
We are getting busy with Shia Iran, a somewhat secular-but-dealing-with-fundamentalist-Sunni turmoil Turkey, the separatist and fairly secular Kurds, and an Iraqi government at a moment of flux bending toward Shia, none of them friends of the Saudis. We are the only friend they have, other than weaker local Sunni states. If they want to make nice with Russia or China, be our guests and see how that goes. In a choice between the US, Russia and China, the US is the least to act solely in its own self-interest.
I believe the Saudis are backing ISIL partly because of the US rapprochement with Iran and the US ramping energy production. The Saudis absolutely don't want a Shia Iraq expanding Iran's sphere of influence. Further, one effect of the energy ramp by the Administration has been to move the foreign policy leverage of the Saud family back a few paces, as the US develops non-fossil alternatives to complete the deal. The Saudis want the US tied down in Iraq with the previous status quo on terrorism and trouble with Iran, and an opportunity to keep Iraq away from Iran. Either ISIL or the US will be sure to prevent that, so they figure they can't lose. The Saudis walk the line between being an Islamic state and a practical monarchy, with problems coming from an internal religious conservative movement. Supporting ISIL gives a visible focus on fundamentalist Sunni interests for the hometown radicals.
The regime change in Iraq makes possible a whole new tack and opportunity for US policy in the region. I was very interested in the positioning President Obama gave this development in his statement. With the corrupt Sunni al-Maliki out of the way, working with the Shiite al-Abadi gives the US more of the Iran-coupled leverage and a natural Shia majority opposition to the Sunni ISIL. How much do the Saudis want a Shiite Iraq? Not a lot. They probably were surprised at the extent of ISIL's military success and turnover of Iraq's regime. The only way they have any remaining leverage is if they cooperate with a US who have increasing ability to influence Shiite direction either for or against Saudi interests. Cut 'em off, says President Obama to the Saudis, or we set Iraq and Iran against you and get increased access to their oil while we continue to develop other alternatives to Saudi oil.
Saudi oil has been a chain around the US neck that the Saudis have been able to yank since World War 2, putting the US into odd positions with a number of players in the Middle East and around the world. With a pre-existing alliance with Sunni Saudi and developing relationships with Shia Iran and a newly Shia-led Iraq, the US can have leverage on both sides, remove the Saudi collar, and possibly be able to use an even-handed approach to reduce the state-sponsored terrorist attacks on Israel and elsewhere.
I think that the president's pause in acting was in anticipation of or seeking just such an opportunity. The bellicose rhetoric serves political purposes at home, while enabling larger geo-political purposes abroad. The rhetoric about arming Syrian moderate rebels is a necessary sideshow to re-state opposition to Assad when the US is really not going to do much about him. My guess is the chatter back-and-forth about more American wars will wind up muted by the alignment of interests in the Middle East providing leverage on taming ISIL without a large direct American military investment while the larger scenario plays out. The key is watching Saudi actions with respect to ISIL. My guess is they fold when they get over the surprise at a nuanced approach by the Obama Administration.