The folks at WP Media team are currently adding support for WebP. The media library is more than just upload a file and put the name in the database. It is also
- all the JS for navigating around the media admin pages (edit, crop, delete)
- generate smaller sizes
- the JS to interface with the editor to handle images (insert to post, galleries, upload)
- gallery shortcode
- compute which smaller size to use
- generate
srcset
andsizes
attributes
As you can see, some of these things make sense for JPG and not for SVG. The people working on WebP are trying to come up with a way to convert from JGP to WebP in a non-intrusive way, for fallbacks and caching and resource usage.