I don’t see it as very likely that we’ll add WebP back as a builtin compression format. Supporting many separate technologies is an added extra development cost.
We will however be supporting custom resource formats later this year (and we’ll keep this feature in mind when we do). In that scenario you should be able to compress the data any way you want.
Another feature I would like to see as a saving for games chasing the last megabytes, is an api to supply a font with font glyphs. That would enable a game to avoid bundling with a lot of font data.