My suggestion is that you first watch this amazing video, and then we talk.
How amazing was that?! The efficiency of Section 9 never ceases to amaze me. When the poster was released a while back everyone was throwing critisisms back and forth saying that Major Kusanagi is not the same unless she looks like she's in her mid-20's and half naked.
People discussed whether she had to transfer her mind into a younger girls body for a mission, among other assumptions brought up to explain why she now looks twelve-year-old.
I already had a great guess from the beginning. Ever since 'Stand Alone Complex', when you watched the intro to each episode, you always fond yourself wondering, "Where on earth did Major Kusanagi come from?" "What's her back story?" Not to mention that in a couple of episodes from back then, they would hint on this with questions/inside commentaries provided from both Batou and Chief Aramaki.
A quick disclaimer (Don't murder me yet) I must mention that I haven't read any of the Mangas at all, and have just followed the series religiously.
So when watching this trailer, I believe my guess was more than right. Seeing Batou with his finely trimmed haircut, and Chief with his not-so-grey hair, this all must be set way before 2029 A.D.
Another aspect that convinced me of this was the use of that iPad looking gadget (apparently a Windows 8 Microsoft Surface Pro, product placement in an anime perhaps?). It seems that technology, though much more advanced, hasn't reached the level that we see in S.A.C. as well as in 2nd GIG. They're not logging in, downloading/uploading information and messaging through their minds. It's all external.
If they show that transition in this particular series of how man ended up with cyber-brains then, I don't know anymore. This series is definitely going to consume my life while it's running.
The mayhem of cyber terrorism starts on July 22, 2013.