It seemed kinda incomplete when I watched it. I mean, look at the BC trailer. It showcased Illidan, the new races, samples of play (those we could've done without).
The WotLK trailer on the other hand...
It's just seemed too much like a fluff piece, a teaser instead of an actual trailer. A montage on the Arthas himself is all well and good (yes, Sindrigosa is badass), but it showed nothing else. The Lich King can't be the only new feature of the xpac.