[ComicGuy89]

It could very well be that they haven't really had a sense of how the direction of this movie will go until now. Remember, Roberto Orci was supposed to produce it, but he left the project early (my guess is that he went to work on Star Trek). It could have been directionless since then (explaining the delay), until the director pitched his ideas.

Now that they've got that key element down, the rest of the production could flow a lot smoother. Optimistically, this may also explain why they've only announced a delay date now: they finally have a clear vision of where this movie will go, and how long it will take to produce.

So I suppose it won't be long before casting begins. They've also been working on the script this whole time, so that should be progressing better now, too.