Probably it will have a very measurable effect. By every day it gets a bit harder to discover such services - if you know, you know. If you have to ask, you have already lost.

Also, AI chatbots outright refuse to give any answer that is remote related to piracy (or any adjacent topics). Since they take over the role of search engines, that's also a big factor IMO.

You could download books I wrote from libgen, before the actual publish date, and the files were ones I created specifically for Amazon.

So I'd assume libgen and Anna's Archive will continue on, operating just as normal.

Nowadays AA [1] is IMO a better choice for users, but aside from that I cannot imagine these changes making much of a difference. There's plenty of ebook sources (Kobo, public libraries, etc) whose DRM are trivial to break (meaning Adobe and, as of a few weeks ago, LPCM). For what little content is exclusive to Kindle, it will just end up like WEB-DL content from streaming services: a handful of knowledgeable uploader with a KU subscription ripping content en masse—and good luck stopping them.

1: https://en.wikipedia.org/wiki/Anna%27s_Archive