I think Blizzard is trying to level the playing field in a lot of ways with BC. Yes, i think a lot more people will roll blood elves over Dranei, especially kids, who gravitate toward "pretty" races (no condescent here, just callin' how I sees 'em). The fact is that the reason there are so many more allys than horde is that 1: kids want to play the "good guys" and 2: kids want to play "pretty" characters like NEs or Lord of the Ringsy characters like dwarves or humans. By "kids" i mean early to mid teens. Blizzard has the facts on this, so they're making the blood elves to try to balance it out. However, a lot of kids will still roll ally because their friends are allys.
Another way blizzard is trying to level the playing field is making pallys and shammys playable by both factions. This will be interesting, as it will create a lot more competition and demand for plate and mail armor on both sides, pre- and post-40. This will also hurt the horde slightly more, because the shammy has proved to be a better PvP class than the pally. Again, Blizz knows who wins AB 80% of the time, and they are trying to even it out.
Lastly, BC is an attempt to correct for class unevenness at 60. At 60, feral druids get gimped, and warriors become arguably the most powerful class. In tests, I have heard that the post-60 rage generation GREATLY favors druids over warriors. This of course may be fixed by the time BC hits, as well as the allegedly overpowering 70 mage.