Unless HN starts supporting sub“HN”s (or starts allowing porn, jokes and My Little Pony-related posts on the frontpage) I don't think it's a viable replacement for Reddit.
It's already got a lot more political stories (though necessarily post-Snowden); HN feels pretty much like early reddit now. Though I do think Reddit morphed its community precisely to avoid just being another in this list (Digg exodus helped that too of course).