I'm with you here. I still can't believe they gave us Castor without Pollox.
Heh... they're probably waiting until PH4 for the Githyanki. What better way to make sure they get a section of the players to buy the book who might not otherwise, by holding back an important and popular piece? Drop the githzerai into PH3... listen to the feedback of the number of people pissed that the 'yanki were not included... then add them to PH4 so that they can get those folks to buy another book (or keep up with their DDI subscription until it arrives).
It was probably that same philosophy that made them hold back the gnomes, halforks, bards, druids, barbarians, and sorcerers for PH2, and the monks for PH3. Never give the players everything they want when they want it... because they won't buy the next thing otherwise.