When using the inbuilt camera app, I have it set to shoot in HEIF, when using PureShot to control the camera better, I have it shooting in RAW.
You still can't output from Photos in HEIF as of yet, they all get converted to jpeg on export.
I know Photoshop can work in HEIF format, but not Lightroom as yet, and again, you'd still be exporting as jpeg for sharing on the interwebz for quite a while yet, until HEIF is fully supported as an image standard through the WWC.