The art of risk prediction is a tricky one. With most problems, the obvious approach to take is to predict a gradually increasing or decreasing level of concern regarding a situation as in 19 out of 20 situations we may have in global politics, that's the most likely outcome. It isn't always the obvious path that is taken though. One of the only people to predict the Arab Spring was the British journalist John R. Bradley who predicted both the revolution in Egypt as well as the wider Islamist direction of travel in the regions upheaval and whose prediction of destabilization in Saudi Arabia no longer seems like an outlier in global prediction. Most experts saw business as usual continuing, until of course it didn't.
Those experts at least have the excuse that none of the revolutionaries warned them months in advance of their plans. It was conventional wisdom in counter-terrorism circles pre-November 2015, that it was extremely unlikely that the Islamic State would be able to attack Europe. This was a decision born of a prevailing wisdom that there would be plenty of willing would-be terrorists in Syria, but that getting them and their tools of the trade into Europe would be nigh impossible.
This despite the Islamic State frequently stating that they had the means and desire to attack Europe well before that period. Two examples are of an interview given to Buzzfeed by an Islamic State member in January 2015 on how the group was smuggling fighters to Europe in order to carry out attacks and the reports of the anti-IS activist group based in Syria, Raqqa is being slaughtered silently who reported that European ISIS members were openly bragging about being soon sent back to their home countries to carry out attacks.
There are many other examples of Islamic State making such claims before, but they were dismissed as merely propaganda. The thing about propaganda is to have credibility, you don't say anything that you don't mean to follow up on. The focus now, however should be not on how we missed things get as bad as they are now, but how much worse they could get.
The noted British terrorism expert Shiraz Maher remarking on the number of plots disrupted in France stated "Good grief. The French are practically fighting an insurgency." The idea that things could escalate further in Europe is taken further by the former National Security Agency analyst and current history professor John R. Schindler who talks of guerrilla war on Western European soil.
At the moment it seems to me, quite unlikely yet possible, things will get that bad, but the possibility is more likely than it was last week before the Brussels attacks. Other seemingly equally unlikely scenarios such as the 9/11 attacks, the Arab Spring and the financial crisis have come to pass. These world changing events, known as black swan events after the book of the same name by Nassim Nicholas Taleb are hard, but not impossible to predict. There are worrying signs that the Islamic State are wishing to raise the temperature of their campaign. The Guardian reported that pro-IS propagandists have been sending text and social media messages en masse to young Muslim men from Molenbeek (the district of Brussels which has been most connected with the organization) that they have not previously been in contact with.
I am reminded of an incident in the early days of the anti-independence terrorist group in 1960s Algeria, the OAS, where that particular insurgency was furthered immensely by the hijacking of the main television channel in the middle of prime time viewing to deliver a propaganda message on behalf of the group. As television was the main form of communication in the late 20th century, so smartphones and social media are today. The reason the OAS decided to undertake their spectacular propaganda coup was to upgrade from a small conspiracy of killers to become a mass-participation movement.
There is a battle for the minds of young Muslims in Europe and it will not be won by listening to shallow and ignorant demagogues like Donald Trump and Geert Wilders who demand for Muslims to be discriminated against. Sadly especially in the Francophone states (which as Will McCants and Chris Meseroles research shows are more prone to radicalisation) there is a tendency to see their Muslim citizens as an unwelcome inconvenience furthering alienation and helping the Islamic State. However bad things get, we are not going to win the fight against the Islamic State by meeting hatred with hatred, but even now, I'm not sure those in power in Europe realise how bad this could potentially get; but be aware, the Islamic State problem can always get worse and it definitely will unless we seriously consider all possibilities.