Way back when, there was speculation that faction ratios would become inflated in favor of the Horde once BC launched since Blood Elves were perceived as a pretty race which would tempt over scads of Alliance players. I believe Blizzard tried to balance the "looks" factor of the two new races (BE and Draenei) in an attempt to not make one or the other the "obvious cool choice" to at least help ward off huge population inbalances.

Now think about these two theoretical new races, worgen and goblin. Right off, there is a MASSIVE coolness gap. Everyone who wants "badass" (not to mention the metric frakton of anthro enthusiasts out there, whether they currently are Alliance or Horde) will IMMEDIATELY drop everything they're doing to roll one of these awesome Worgen.

If Alliance exclusively gets the awesome, tall, way-cooler-than-BEs-ever-were, bad-ass Worgen and the Horde gets the short, unattractive, smarmy little green dudes (as much as I love them!), there WILL be a *massive* faction population imbalance in favor of the Alliance...and honestly, I believe that this would be a far greater sin in Blizzard's eyes than a couple new races not being instantly recognizable as Horde or Alliance by their silhouettes alone.

Therefore, I predict BOTH factions will get access to Worgen *and* Goblins. It just makes sense...and I don't think it would be fair otherwise!