The development of this highly portable cruise missile is not surprising. Throughout history, there has been a never-ending race between advances in offensive weapons technologies/capabilities and improvements in defensive technologies/capabilities. That miniaturization and portability, which have been pervasive as technology has advanced is occurring on the military front is no surprise whatsoever. Had efforts not been underway to develop smaller, more mobile weapons, that would represent a striking anomaly. That these weapons could represent a potentially disruptive breakthrough also fits the experience with the pervasive rise of disruptive technologies across sectors/industries. That the march of technological advancement might see military applications arise in the area of nanotechnologies is a realistic long-term possibility and such nanotechnologies will create real challenges from a defensive standpoint.
IMO, military planning should never assume a static or near-static weapons environment. Instead, as in this context, defensive military capabilities will need to leverage information/technology so that the ability to respond to threats will need to move ever closer to real-time. Technology won't be frozen in time.
They will also need to be continually cognizant of the rise of disruptive technologies that have the potential to radically shift existing technological advantages. A future innovation might give the state achieving such an innovation a qualitative edge in at least one aspect of military power. There is even a chance that some breakthrough or series of breakthroughs could broadly alter the existing global balance of power, as has happened throughout the course of history.