Google's Gary Illyes confirmed at SMX West that they have at least one team using "rel-author" and that he recommends leaving the markup on your website if you haven't already removed it.
Authorship markup and the displaying of the author name in the search results was dropped in August 2014, following the removal of the author profile image just before that in June 2014. An example of the old Google Authorship in the search results can be seen below:
John Mueller, at the time, stated that the authorship information wasn't " as useful to our users as we'd hoped, and can even distract from those results." According to Mueller, and what most likely reinforced their decision for removing it, was that removing authorship had no effect on click through rates in tests carried out by Google.
This is not the first time Illyes has suggested that you should leave the Authorship markup on your website. Back in October 2015 at SMX East, Illyes said to "leave authorship markup on the page, never know when the team will start using it again."
The latest statement Illyes made on stage at SMX West was confirmed by MyCool King via Twitter:
With the issue being mentioned twice in just six months, it is worth adhering to this advice, and perhaps implementing "rel-author" markup if you haven't already done so. That being said, according to Barry Schwarz, Gary Illyes added that " that it might not be worth adding to new pages but if you have them on old pages, keep the code there."
We suspect that if Authorship were ever used again in the future, there would be an announcement about it. Therefore, this is not something you should overly be worried about at this stage.