with edge moving the chromium... the only major user base not capable of viewing webp files is safari users on ios devices. or basically any browser using the same rendering engine on ios devices. of course, there are tons of safari users on macos as well but that number is probably not as large as the number of iphone/ipad users out there but this would mostly change from one forum to another.
i am just glad that mozilla ended up supporting these file formats few months ago.