Would like to thank you for that post, I've been trying to find the details on why it was delayed but because their was no official thread made on it and these answers are all over the place it amde it rather tedious!
If you check the Dev Tracker every day you can usually easily see what the Devs are saying about a particular issue. Checking the Dev Tracker is the first thing I do when I come to the forum each day.
As for the delay in the Nebula, Dstahl stated it had to do with the fact that the code in the Nebula was part of a new code string that hasn't yet been introduced into the game. If the Nebula didn't use the new code string it could have been introduced already.