I tested exporting an InDesign layout with .webp images. They do export, but the images are converted to PNGs--even when Image Quality is set to Use Source Images (when available). Justin is going to take a look to see if it's possible to support exporting them.
I did notice that although InDesign supports placing .webp images, InDesign doesn't support exporting them. I'm not sure if that will affect in5's ability to export them though:
I'll keep you posted.
Good news! :)
Exporting and preserving .webp images will be available in in5 v3.8.12. Because this is a web-specific format, .webp images will get copied to the output regardless of whether Use Source Image is selected (unless the image is cropped, rotated, or has FX applied...then it will be re-rendered as a PNG).
There's no ETA on the release, but you can check when the new version of in5 has been released by doing one of the following: