Some web browsers support these technologies. Recently I added support for them in Roundcube. Here’s a short description what you can do with these right now and what are the limitations.
This image format is supported by Google Chrome, Opera and Safari. So if you open a message with such images attached you’ll see them.
If you have ImageMagick installed with WebP support built-in (which is not the case on all systems, e.g. Ubuntu) you should be able to see WebP images on other browsers, as they would be converted to JPEG. The same applies to thumbnails generation.
In Roundcube we use also PHP-GD module for image conversion, unfortunately even PHP7 does not fully support WebP.
This standard is supported by Firefox and Safari. So, if a HTML message contains MathML code now you’ll be able to see them nicely formatted.
At the moment you can’t create MathML equations when composing a message. On reply/forward you’ll see broken equations (in the TinyMCE editor) too. So, only preview works.