No, it's not going away after 2012. That's wrong. It's on the deprecation list. The current plans are that once something goes on the deprecation list it should only last two versions. For mirroring that would mean 2012, 2014, vNext and gone. But I'm not sure that Microsoft is enforcing that.

I wanted to get this post up quick to refute some bad information. I'm spinning up my 2014 virtual server and I'll check on mirroring for you there to get an absolute read on it.