I can't speak for the big guys, but I'm seeing more smaller Flash game devs make the transition from Flash to Haxe, mostly for the ease of porting to mobile/HTML5.
I've been making Flash games on and off since about 2007 and finally made the transition to Haxe with my latest game [1]. As others have commented, it's not perfect yet (i.e. some features aren't yet available on all targets), but I'll never be going back to Flash now.
Other than "Papers Please," who is using Haxe for production (i.e., making money on products built with it), and for what?