An update to the Google Photos app just rolled out, bringing the current version number up to v1.17. This release is pretty straightforward with just one notable change: photos can now be edited in a non-destructive fashion. In other words, you can make changes to a picture and still return to the original version if you like. That feature alone is certainly enough to make this a worthy upgrade, but a teardown provides some good clues about features that are probably coming in the next couple of releases, assuming they're not already here.
Official Changelog Posted
Google just posted the official changelog, but it's more of a roundup describing features from the last few weeks.