No 9/11 doesn't necessarily mean no Bush victory in 2004. His numbers weren't soooo bad before 9/11, comparable to what they were before the election. Unless his domestic plans end up being really terrible there's not really a solid reason why he can't win. Now, the Great Recession might occur around the same time, which can either change the impact of 2008 and give it to the Dems or leave Bush's GOP successor (hopefully not Cheney) with a major crisis. If Ron Paul runs we'll probably still see the Tea Party, but they probably won't be as strong without someone like Obama being in the Oval.
When it comes to the Middle East, the Arab Spring will probably still happen. People are still going to fight against dictatorships and for democracy, besides the War on Terror's butterflies for the extremist movement. This means that Saddam's going to have to deal with protesters just as Assad will, (and he'll get sanctioned because he'll be as brutal as always) and we're going to still see a lot of instability across the Middle East. Hopefully al-Qaeda and other extremists don't win out over the democrats, though.