Is this planed for near future?
Since webkit does not support Webp, OffscreenCanvas is the only performant way to convert such images on a background thread. Not having Offscreen canvas means no Webp (or any other image format not supported y Safari).
OffScreen canvas will also enables mapping engines such as Mapbox to render tiles on background threads - significantly speeding up maps.
It would be great if Webkit were to implement Offscreen canvas - it will unlock huge potential for the web.
Thank you for considering it a priority.
I'm working on updating/finishing Zan's patches.