I didn't see any mention of deleting photos that were over the limit. Hopefully they do what Flickr used to do, which is make only the last 1000 photos publicly visible.
From the home page.
Yahoo might have been able to afford it.
Otherwise pro user still paying for it. Everyone else didn't. Why should they care what people think of them who didn't pay anyway?
A possible reason why someone running a website should care about keeping stuff up is to avoid link rot, to me it feels like part of bejng a good Internet citizen is to ensure that a change to your website doesn't break other websites or links where possible and reasonable. (if people want stuff removed, then that's fine though).
However, it might be that it's too expensive to even just keep stuff up, so fair enough, but if that is the case, I feel more warning would have helped a bit here.
EDIT: correction, it says they'll first be hidden for about a month, then they will be "actively deleted".
It does say that if you were over 1000, you have a month where you can't upload any additional photos, but before they start deleting photos.
> Free members with more than 1,000 photos or videos uploaded to Flickr have until Tuesday, January 8, 2019, to upgrade to Pro or download content over the limit. After January 8, 2019, members over the limit will no longer be able to upload new photos to Flickr. After February 5, 2019, free accounts that contain over 1,000 photos or videos will have content actively deleted -- starting from oldest to newest date uploaded -- to meet the new limit.