Debatable? The facts speak for themselves.
For the past few decades Saudi has been under the military umbrella of the U.S. Irrespective of how the Saudis and other Gulf states 'perceive' the U.S., the fact remains that they rely on the U.S. for regime survival and external security. The seeds of this strategic relationship was sown following FDRs meeting with King Saud in 1945 and during the Cold War this relationship grew in importance. This strategic relationship - despite deep political differences - benefits both countries and is still in place today. Despite its shift in focus to the Asia Pacific region, the U.S. is still maintaining its presence in the Middle East and until this changes, the Saudis have no reason to resort to something as drastic as getting nukes.
The past history is good, but only the future is all that important. But this is the era of the Reset, the defense draw down, and the Re-alignment, so the question is not how did the US do for the last 50 years, but what can and will it be willing to do after 2020?
If they are not confident that the US will still be capable of defending them after 2020, then the past is irrelevant.
And you're suggesting that the documentation and scientists are hidden and are just waiting for the right time for a willing buyer to emerge? If I recall correctly, the testimonies of Iraqi scientists who were debriefed/interrogated by the Americans and the IAEA indicate that the bulk of most the vital documentation relating to the design and manufacturing of WMDs was first hidden and later destroyed on Saddams orders. Some were also smuggled out by scientists who fled Iraq.
Most of the Iraqi scientists and engineers who worked were never identified. So naturally we don’t know where they ended up or what they are doing now. Hopefully we identified and found the critical ones. Personally, I think a lot moved to Syria and Libya, and probably some eventually to Iran. Any remaining in Syria are probably shopping hard for a place to move to.
Was it all truly vital material? In any manufacturing enterprise 97+% of the physical documentation is unrelated to design, or additional copies. Saddam would certainly have wanted to destroy the production records and the records of any personnel that would allow the Americans and the IAEA to reconstruct what and how much he had done, but the vital design files would have fit in a large truck, or a couple hard drives. So we don’t know how much of the knowledge needed the ones who fled took with them.
Irrespective of whether Khan was a front man or was acting on his own, Pakistan no longer can be relied upon as a source of nuclear technology. The Pakistanis realise the danger this created for them and understand that whatever short terms benefits that can be derived from selling technology is outweighed by the long term negative effects upon their country. And yes, the Khan network was the main source of technology in the past. Apart from North Korea, there was nobody else.....
Again you're making the assumption - based on past history - that Pakistan will again be a source of technology or missiles and will repeat the same mistake it previously made, despite such a move being highly detrimental to Pakistan's national interests - not to mention the fact that it still needs U.S. financial aid and diplomatic support on the world stage.
Pakistan made the mistake of underestimating the profit/loss ratio, but they will not necessarily be repeating that if they sell to the Saudi’s, or a consortium build around them and other Sunni Gulf States. Increasing the profit by a couple orders of magnitude could eliminate the need for US financial support.
North Korea doesn’t have a proven product to sell, so they are out. But the Chinese seem willing to sell anything to anyone, if the price is high enough.
With regards to the Sunni inter cooperation, why are you assuming in the first place that Saudi and Iran even consider Iran a 'foe'? They may be long time rivals, have jostled for power and influence and have conflicting interests but both countries do not consider each other as 'foes'. Saudi and the rest of the Arab states may still deep harbour distrust and fear against the Iranians but the geo-political situation is way different than it was in the 1980's or the 1990's, the Iranians are no longer calling for the Arab masses to overthrow their 'corrupt' and 'decadent' rulers.The Saudis may welcome strikes on Iran but they do not want to see regime change in Iran caused by Western military intervention and they do not want to see Iran's infrastructure devastated, the way Iraq's was by an air campaign, as this will create instability that will affect the Arabs - they have seen the mess that was created in Iraq.
The Iranians are no longer calling for the Arab masses to overthrow their 'corrupt' and 'decadent' rulers? That’s a new one. When did the change take place? Is it internal, or just in the western ‘press’?
The Saudi’s are probably more worried about an air campaign like in Libya, which is probably inevitable if the western powers feel forced to go after the Iranian nuclear facilities, than they are about one ending in a ground campaign like in Iraq, which is totally unlikely.
A nuclear armed Iran is very different politically and strategically from one that is not. If give Iran the ability to open any conflict with a decapitation strike, so that ,even if the US intervention kicks them back into Iran, there will be a regime change in Saudi Arabia, or whoever they target. That should worry the House of Saud more than simply the ability of Iran to wage war on Saudi Arabia itself.