This is a poorly considered proposal and should not go in core. The developers of this project clearly do not have a good understanding of how most site owners actually use WordPress.

Media libraries are already overly bloated because of the massive numbers of thumbnails that are generated automatically (it’s not at all uncommon for sites to generate 30 to 50 thumbnails for every image!). Most of those thumbnails go unused and take up expensive disk space. And this proposal will nearly double that usage.

This is going to effectively take every media library on every site and multiply its disk usage by ~1.7. (The changes will currently only apply to newly upload images; however, when you regenerate thumbnails it will apply to all of those.)

This is a clunky way to implement WebP — just doubling image files, most of which won’t ever even be used. And, what happens when AVIF (which is potentially a better format) gains widespread adoption? Do we create additional thumbnails for that too?

There are also significant conflicts of interest. WebP is a format that Google Created — and it’s Google Engineers who are leading the Performance Team. This proposal is designed to serve Google’s interests (making it easier and cheaper for them to crawl the web). And the increased cost for all the additional storage space needed will be borne by site owners, not by Google.

They say they have consulting the hosting community — but commodity hosts like Bluehost, Siteground, and Dreamhost (the “official” recommendations here https://wordpress.org/hosting/ ) will just tell people to buy more storage space — increasing their profits.

I encourage everyone to read the comments on the proposal and chime in there.https://make.wordpress.org/core/2022/03/28/enabling-webp-by-default/

This SEJ article also pulls out some of the key issues reflected in the comments:https://www.searchenginejournal.com/wordpress-proposal-backlash/