I just had a thought. I think the Easter egg for this map may be about the original 4 and possibly bringing them back to earth. I was reading through some other forums about Die Rise when I thought of this. Now this is probably incorrect, I'm most likely way off but I just thought I would share my idea with you.
My reason for thinking this is because of the name 'Great Leap Forward.' This name is similar to the first man on the moon Neil Armstrong's statement "one giant leap for mankind." This leads me to believe Great Leap Forward is relating to the moon. Also, I believe the developers may be thinking it is a 'great leap forward in regards to the storyline and the general gameplay of zombies. TranZit, or Green Run (whatever floats your boat), in a way was a taste of what is to come, basic perks, WW, Easter egg, etc. I don't know about you, but I didn't think the Easter egg really solved much in Green Run compared to previous maps, and I think we may start to see a large advancement in the storyline now. Treyarch may be expecting a positive reception from this map. They seem to be more secretive about this too. Usually The achievements are leaked or updated/released by now and there hasn't been a trailer, yet. This may be because they do not want to give anything away. I believe this map will be where things start to get interesting, where we will be able to witness treyarch's full potential.
I think the name 'Die Rise' may also mean to be taken literally, of actually rising up, more than just the skyscrapers. I would love for this to actually happen. This would mean we would definitely play as the O4 eventually in the future.
Ok thats it, so what do you guys think? The further I get into writing this, the more uncertain I am about this idea. Oh well. I would appreciate your opinions on this, I look forward to hearing from you guys.