Of course. I'm referring to a hypothetical distant future world where a random, moderately intelligent lone wolf, with any motive or no motive, could potentially inflict nightmarishly efficient and asymmetric damage given the resources, knowledge, and technology at their disposal. Let alone a group of such individuals.
Right now, terrorism is a very minimal risk for an average individual. Even if every single US terrorist attack caused as much death and destruction as occurred on 9/11, it still would be. But what if, due to future circumstances we can't currently predict, every attack had the potential to be many orders of magnitude worse than 9/11, even if there's only a single perpetrator, or just a few? Of course, we'd cross that bridge if and when we get to it, but, in general, the cost of terrorism/mass murder will continue to decrease, and its force-multiplying potential will continue to increase.
In this hypothetical case, it makes no difference if the terrorist is from a different country, or your own country, or motivated by ideology or just a Joker-esque mentality or because their girlfrienf broke up with them a month ago. If it really could take just one nut to cause more suffering in a day than Hitler or Stalin caused in their entire lives, we'll need to rethink the role of government and the boundaries of privacy. Right now, your description is accurate, and it probably will be for the next 40+ years, but the distant future is tricky to predict. Even if the odds of an attack occurring remain roughly the same, the overall "expected value" of terrorism could still skyrocket.
I'm particularly worried about hypothetical new fringe, cult-ish elements like Aum Shinrikyo or even the Manson Family, rather than an organization akin to al-Qaeda or ISIS. I've long harbored a persistent fear that Aum Shinrikyo may be a prototype or inspiration for a future organization or movement which could thrust all of human civilization into darkness through relatively little effort, and before anyone fully realizes the risk (like the risk of planes as suicide bombs before 9/11). All of these copycat mass shootings - while not currently "scalable" (in the worst way possible) - don't inspire optimism on that front, either. Al-Qaeda has specific political goals and strategies, but what about people who sincerely just want to kill every or almost every person in existence? How do you deal with that? Those people scare me far more than any violent religious or political extremist, when considered in the long run.
No matter how much you try to remediate disenfranchisement and discontent and mental illness, some number of people like that with violent urges will always exist. And some people will also perpetrate mass murders without sharing any of those charsct. Aum members didn't exactly seem to be the pressured underclass:
>Aum Shinrikyo recruited approximately 300 scientists with degrees in medicine, biochemistry, biology, and genetic engineering.
>Around 75 researchers were discovered who were working on radioactive materials and other nuclear related studies. [Materials] found in the raids indicated that Aum members measured radioactivity levels at a cult compound
They had esteemed professors and scientists manufacturing biological, chemical, and nuclear WMDs to cause. These weren't powerless people without hope; these were powerful, well-off people with a fervent hope for a new world forged from the ashes of the one they attempted to annihilate.
They may have been very close to killing tens of thousands of more people than they did, if not for a few mistakes, and happenstance of bystanders noticing their dispersion devices pre-activation on several occasions.