The many "copycat" and "self-starter" groups that have been "inspired" by al-Qaeda and that have sprung up in England, Spain, Indonesia, and elsewhere will continue to pose the threat of attacks. The threat is likely to be more acute in Europe than in the United States, where the Arab-origin and Muslim population has been far better assimilated and far more patriotic, despite pressures and provocations, than elsewhere. Politically motivated violence has been a reality of modern life, and will continue to be so. The news, and where it happened, reinforces this point.
I don't believe there are particularly significant moral or political gains to be had from declaring victory in a war on terror that was a complete fabrication to begin with, but it is notable that this groundswell of support for al-Qaeda is coming from Islamic communities in Europe, not in the United States. People often forget that the September 11 attacks were planned and executed by a group that was organized and based in Europe. For all the braying of intolerance we hear from certain politicized media outlets, it's evident that the American culture fosters a far greater sense of nationalism and belonging for first generation immigrants than in Britain, where the culture of segregation has led to continuing racial tension between Muslim communities and other groups.