Not without doing what you've tried. Think there are some online converters too but if you have a lot of images...
I just love "standards" like this format. They make everything so...standardy.
If you download a photoshop plugin for WebP like this one
then you should be able to use File>Scripts>Image Processor to batch the WebP files to a file format like Jpeg.
If you want to have a smaller file like Save for Web produces then you could download the Image Processor Pro, which
has a Save for Web setting.
It is quite ridiculous that Photoshop still does not support WebP completely. WebP is an excellent file format (in particular for mobile app development, for example), and not supporting opening WebP images directly in this day and age is, quite frankly, just plain silly.
Anyway, if you are on Windows, download Irfanview to open WebP images, and convert to a Photoshop usable file format. Irfanview includes a very fast batch processor (which is by far quicker to process images than Photoshop).
If you are on Mac, XnConvert is an alternative.
Another option is PhotoLine, which opens and saves WebP on both Mac and Windows.