WebP seemed fairly pointless; its advantages over existing formats were slim, it had some disadvantages, and lacked any compelling new functionality (e.g. good HDR support). Basically it was pretty "meh."
Given the huge effort required to get any sort of widespread adoption of a new format—and without widespread adoption there's little point unless you've got some unusual features (which WebP didn't)—I'm not sure there was ever much chance WebP would go anywhere.
I'm generally no fan of Microsoft, but MS's new image format, JPEG XR†, seems vastly superior to WebP in almost every way... and it actually does have compelling new features.