If WebP takes off and becomes a major image format, I would also like to see support in PB. The file sizes are smaller, so it'd be useful to reduce bandwidth.
Since it's a lossy format, I'd be much more interested in encoding capability than decoding. Not much point loading degraded images, as opposed to saving them.
But of course WebP is a long way away yet.
EDIT: Maybe not so far off: the first program to support it has been announced:
PixelMator.
JACK WEBB: "Coding in C is like sculpting a statue using only sandpaper. You can do it, but the result wouldn't be any better. So why bother? Just use the right tools and get the job done."