Nearly all the images of nearly all the posts will suddenly disappear.
I suspect, recovery work will start on the spot, probably by asking for the local user caches of the readers, and digging in the archive.org . But it won't be ever complete.
Does the SE have some local backup of the many imgur.com images?
Yes I know that the imgur.com, being a big global provider, is not expected to suddenly die. Even short breakdowns are unlikely. But, it hosts a very large repository of images, it is essentially a large static file service, with little direct user interaction. This makes their business probably lesser economical, compared to other global services with this size.
Should maybe the SE host its own images at least?