Tweet from February from Google's WebRTC Project Director citing the change. [1]
It's definitely coming to desktop Safari. Doubtful we'll see it on mobile Safari, but fortunately on iOS, WebRTC support is already possible in-app.
While I understand there's an argument to make on standards for them supporting it in mobile Safari, a mobile web browser is really a lousy place to build software like this. Customers are going to be much happier using a native application. We could certainly get into a discussion on what Google is doing with the mobile web on Android that would make mobile Safari support more important, but Apple is not going to be moving away from installable Swift/Objective-C based applications for the foreseeable future, and that's going to remain the best implementation route for a while.
It's possible on iPad, but not iPhone.
I'd be surprised if WebRTC isn't on the list to be a major feature of Safari in this fall's OS X 10.12 release, which will be previewed at June's WWDC.