Aside from man power maybe being an issue, what would one thing coming out have to do with the other?
It's a marketing thing, and since Sins:Diplomacy is already out, its updates take priority. This first month up updates is vital for a new game...if we can keep players happy and playing, it ensures a positive experience and fond memories. We drop the ball at this stage and they stop playing AND hate us. Never a good combination.
On the bright-side, we get another week to polish and add features, so 1G is gonna' kinda' blow everyone's brains out their skulls!!!
(hopefully)
(...and hopefully not literally)
edit: And an IT thing, as the Frog has spoken.