What we need to understand with the Middle East is the 'bigger picture' as defined by Osama Bin Laden and picked up and run with by ISIS. The plan is to topple each of the countries within the Middle East one by one to create the Caliphate. This action is not for religious reasons, but to control the vast oil and gas reserves that these countries hold, in doing this they can control and basically cripple the economies of the West. The UK gets much of its oil and liquid gas from this region.
The terrorist attacks threatened and carried out in the west are probably diversionary tactics whilst their main objective carries on.
This is why western governments are striving to find alternative power sources ASAP.
Those who travel to Syria for religious jihad are being misguided, the fight by ISIS is nothing more than economic control by the Sunni Muslim extremists. One saving grace may be the tribal and sectarianism of the region.
ISIS did not start the problem in Syria, this started by one of two hypothesised issues (over zealous military or push for social reforms), however to the dismay of many Syrians, they paved the way for ISIS, who were already in Iraq to move in and so began their caliphate bid.
If ISIS is defeated it may reduce the global risk, but some other fanatics may pick up the baton as ISIS did with Al Qaeda, and the internal conflict within these countries aside from the ISIS fight will probably continue due to multi-sectarianism within the region. This multicultural/sectarian tension may now be being stoked within the west, people do not lose their prejudices by moving locations.