AllFacebook notes in one of its recent post that the network is testing addition of a ‘make profile picture’ button to photos.
You could see this photo and feature, as shared by Karthik Verma of Sociobits.
You could see that just beneath the photo a option is there to make the photo as new profile photo. Similarly the feature is also being shown like this:
Facebook seems to be working on multiple changes at the same time with bringing so many changes to its CSS (design format) for pages and profiles.