I'm starting to think it's shifters. There's the Cliffwalk Archer in DoD (the new mini set), and a "Werewolf Champion." Shifters also have a lot of potential for level-based acquired racial abilities, which are integral to the new edition. The only trouble is that elves kind of fill the "close to nature" archetype, but I can see how they could represent two different aspects of nature. Edit: The other thing is that it could be a gesture towards the Druid-lovers out there. They do have the shapeshifting thing going on.
The only problem is that I half-expect the new race to have a connection to the Shadowfell, which would mean something...well, spookier. The shadar-kai could work, but I'm not sure if they have the capacity for iconic status. An undead option could be interesting. I would be on board for a Necropolitan "racial" option (though it might be too uncomfortably close to WoW's undead).
Edit: The "Necropolitan" template was in Libris Mortis. It was an acquired template that turned you into an intelligent undead (basically, it gave you the undead type).
Edit2: The other problem with Shifters is that White Wolf has a well-known Werewolf brand, but I think they are sufficiently removed from that concept that it's okay.
