The current goals of Islamic terrorism and less easily defined and less easy to fulfil
They're completely incoherent. Al-Qaida would like a big ass fundamentalist Islamic Caliphate stretching from Pakistan to Spain, but the fact that they have such an aim just shows how completely detached from reality they are. The demands of other Islamic extremists are more limited (e.g. destroying Israel; driving the U.S. out of the Middle-East). We're hardly talking about a unified movement with a specific aim here (unlike Western 'nationalist' terrorist groups like the IRA or ETA).
What people in the West frequently fail to recognise is the fact that the Islamic world is deeply divided. As we see in Iraq, the Sunnis and Shiites hate each other with a passion. Muslims killing other Muslims is far more common than Muslims killing Westerners (or vice versa), whether in terrorist attacks, or in guerrilla warfare in the ME.
At that point all bets are off and we have a WWIII on our hands.
This is just not going to happen. The Cold War had the Soviet Union as a coherent, organised enemy. No such entity exists on the part of radical Islam.
The closest we'll likely have is a major regional war involving Iran. That could go very badly, especially ir Iran gets nukes in the very near future, but it will not be
nearly as bad as would have been a full blown war between NATO and the Soviet Bloc in the 1970s or 1980s.
As Winston Churchill put it, World War IV will be fought with rocks
I'm a huge admirer of Churchill, but I'm pretty sure that Albert Einstein said this, not Churchill.