I don't know about the future, but it used to be that sardines were a fish that was not over fished because they weren't that popular. Of course that could change.

Anecdote, not data: I picked up the habit of eating sardines from my Dad who is 97 years young. It's not that he doesn't eat bad stuff, its just that in my lifetime I see evidence that many of the things he ate were healthier than we thought.

"Cannery Row" in Monterey, CA, famous from John Steinbeck's stories set there (including an eponymous book), was initially a sardine fishery opened in 1902, peaked in 1946 at 142,282 tons, falling one year later to 26,818 tons. Most canning factories closed in the late 1940s and early 1950s. By 1973 the last cannery closed, and was no longer packing sardines but a mix of tunay, anchovy, and mackerel.

<https://en.wikipedia.org/wiki/Cannery_Row>