All jokes aside, this was a quote from Abrams:
"A final step taken was to script out all of the major long-running plot elements, including the show's finale, prior to full-time production."
This show has been heading on a specific path from the beginning.. getting there has been more than half the fun! Abrams contrasted this to the process used in Lost, where ideas like character flashbacks and the hatch from the second season were introduced haphazardly and made difficulties in defining when they should be presented to the viewers. Instead, with Fringe, they were able to create "clearly defined goalposts" (in Itzkoff's words) that could be altered as necessary with network and seasonal changes but always provided a clear target for the overarching plot. These approaches also allowed the team to introduce unique plot elements to be introduced in time that would have altered the show's fate if known at the start.
"There are certain details that are hugely important that I believe, if shared, will destroy any chance of actually getting on the air."
The producers have stated that when the show's mythology is introduced, it is not simply there to tie episodes together, but "to provide answers that generate consequences"
This post was edited on 10/3 at 3:52 pm