Except the fact that trolls can shapeshift, and also Alliance/Horde race/class combo's will be more balanced if they do these new ones...I think ;)

"You guys are idiots if you think NE Mages is going to happen."

http://www.blizzplanet.com/blog/comments/cataclysm_the_return_of_the_highborne/

"Troll Druids would never happen either. For that to happen they'd have to have another Alliance race druids too, and none of the alliance races (Except maybe dwarves) would make sense."

Worgen druids.

If Wogren are the new alliance race, it is almost a sure thing Druid will be an available class, thereby giving Alliance two druid races.

Even with all these new changes, the number of class/race combinations across factions are still not even. (eg: Ally has more paladin races, horde has more warlock races)

Why does everyone think that Trolls cannot be druids simply because the Alliance would then only have 1 Druid race?

It doesn't affect class balance or game mechanics in any way. Raids wont become easier for The Horde because of a deadly Tauren and Troll druid combo team, it's purely cosmetic.