Free Associating: Tieflings -- The Mark of Cain, the Faustian Bargain, the shame that continues for generations, discrimination based on appearance. There is a lot of room to work with some memes here. This is where we can park the "I am discriminated against though I still fight for good" that those angst-based White Wolf games got a market share on (Vampire, Werewolf, etc., made money).
Dragonborn -- Martial good guys, strong, old empire, related to ancient sentient beings (Dragons! As in Dungeons & . . .). And this time they do not end up either butt ugly or terminally shy. They are actually natural leaders (in many senses of the word). Thus you get the "Big Tough Hero" mold that is universally popular. And you don't have to be a product of rape at some point in your ancestry!
Heck, people have wanted to play the Dragon since 1st ed., otherwise Gary Gygax would not have had to write against the idea in the 1st ed. DMG itself.
Come to think of it, Torog becomes the God that has a legit portfolio (prisoners being kept in a dungeon) but goes too far...perhaps he wants the whole *world* to be a Dungeon, because no one can be trusted with freedom. Hmmm...Dungeons. As in ...& Dragons.
I think the only problem with my old guard friends is that we are so damned jaded that we tend to look at the racial stats first, and flavour second. Those that want the strength bonus *would* play a Talking Toaster if it was the strongest race, and worry about the flavour later.
On to other races:
Eladrin -- Fairy Tales, this will strike a cord. And it has been critically underdeveloped in D&D, so I am pleased to see more Fey love in this iteration.
Elf -- Forest archers. Robin Hood, Legolas from the movie, etc.
Half-Elf -- A harder sell, but the possible "Face" character. Tanis Half-Elven from Dragonlance, Aragorn has some elven blood and ended up as King, etc. I actually see Half-Elf as a bit of a weaker theme than most and was mildly surprised to see it in there. I see it as a bit of a sacred cow.
Halfling -- Well Bilbo Baggins and his nephew are the Big Archtypes here, but there is room for those that like small sneaky characters that outwit larger (and usually dumber) opponents.
Dwarf -- Miners, Fighters. And since Fighter is now more the Defender Tank than the Offense dude, Dwarf fits the mold rather well. I noted the "five o'clock shadow" on the female dwarf picture as a compromise on the "do female dwarves have beards" debate. The new trope is that they started as a slave race (like the Gith) so that may cause a change in how the race is perceived in 4e. Mind you, they also have the "wise elders" thing going that makes them good clerics. Durkon! Order of the Stick goodness, but that won't attract new people that haven't gamed before. Hmmm....
Humans -- The versatile race. And still the standard for people that don't want to play the races that they don't "get". Human is never a bad choice for any class.
So of the races, I would say Humans, Halflings, Dragonborn, Tieflings Elves and Eladrin will prove popular among the new players/buyers. Dwarves and Half-Elves less so. But I could be totally wrong on this one. Let's see what happens in the next decade.
