May be veering off thread here, but I too think the Arab Spring was inevitable. It may not have happened in 2010, but its likelihood would increase every following year. It's main reasons might have been food prices, or Wikileaks' release of the State Department's embassy cables, but its main facilitators were Facebook, Twitter and Youtube, along with the IPhone... And those will only get more popular over time. So in the end it took just one suicide of a desperate youth in Morocco, shared on the new social media, out of reach of the state censorship, to engulf the whole country in protests and then spread out to the neighbors. Sadam being around or the US invasion not happening would not change that.
This being said, if Saddam would still be in power, I doubt that the Arab Spring would ever go more westwards then Egypt. Saddam and Assad, even if not direct working together, would between them suppress every insurgency just by keeping the respective rebels from going across the border to regroup. So we would probably only get a North-African spring.
No insurgency in Iraq and Syria and no porous border between them might however also butterfly away ISIS.