One, while I haven't played in the beta I do know that Blizzard stated that in most conflicts the Horde and Alliance were supposed to give as much as they take.
Also, if the new music is any indication, I think the Horde being a rising power bent on conquest is supposed to be a major theme.
And the Alliance being beset upon on all sides and trying to fight for their homes and families is also a major theme.
I don't think it's a sign of weakness in the Alliance, the Alliance was simply hit harder by the cataclysm and the Horde took advantage. No, the Horde isn't about to destroy the Alliance, Blizzard isn't about to completely alienate half their playerbase.
Also, I think a lot of it has to do with the way the questlines were rearranged. Areas which both the Horde and Alliance are supposed to quest that aren't dominated by a neutral faction show fights breaking out between the two sides. Areas that were once used by both factions but now only one faction quests in has that "winning" faction destroy the other one. Like Southshore being destroyed in the Hillsbrad Foothills, on top of the fact that it primarily served as a hub for high level Alliance players to gank Horde questers and the fact that the Alliance players that WERE there to quest were a whole 10 levels above the Horde questers.