Psikus
Explorer
Dragonborn are, by far, the most played race in my group. I think they're definitely here to stay. As for tieflings, we have only had one so far. I like their new appearance and unified origin, but we just don't have the kind of players that should go crazy for them (i.e. drow players). That said, I'd bet that the dark, tortured race that will get real traction this edition are Shadar'kai (and they aren't even in a PHB yet!)