I’m sure Instagram will take action. Already, I’ve seen they are starting to “delete” or perhaps, relocate expired images. If I go to the URL of an image that was once on someone’s Story, I now get a “Content not found” error. Instagram must be slowly running a batch process to move these files, since the links to images recently deleted still work (for now).
Facebook/Instagram have been pretty strict about this sort of authorized usage of their APIs in the past, and I’m surprised I haven’t received a Cease & Desist Letter yet.