Let’s think this out. Bear with me…
Peter eventually uses the time machine at the end of season 3, creating a paradox in that He and Walter build that very time machine in 2026 to send the pieces back in time millions of years ago, where upon the 2008–2011 Fringe Gang will find and gather the pieces (not knowing it was themselves who constructed it and hid the pieces in the past), to then later be used by Peter to… a continuous loop.
But.
We’re missing the actual plan. When Peter comes out of the machine, he’s elated and says he “built” a bridge between the two universes to work together and… he fades away.
Here’s what I’m thinking, although there’s nothing yet to confirm it.
Since Peter used the machine to get to 2026, it became apparent they, themselves built it. Peter told Walter, that this time, he has to do the right thing, and finally let him go. Walter finally accepted this.
But we don’t know what they intended to happen. Did Peter say that because he thought they needed to change the timeline as we see it now, where he’s not supposed to live past age 10? And if so, how would that work, since it was an Observer who saved him. OR… was the machine designed with a dual purpose, to bring Peter forward and backward in time and to reverse the damage it’s wreaked over the last 15 years but creating some kind of bridge? Or perhaps they were led to believe they designed the thing by the Observers as a trick to “set events straight” and make sure both Peters died that day, by choosing not to pull him out of the ice.
Either way, look at it from the point of Peter. He seems to remember everything. He hasn’t had any dialog about this yet, but what exactly did he experience when he “fluttered out of existence”?
I’m thinking one second, he was telling the gang about the new UniBridge, then the next thing he knew he was gasping for air at the very spot he drowned in this new universe.
Peter’s been preserved. Maybe because the machine booted him out of the blue and red universes he knew, and tossed him into an altogether new one where he died, because the Observer didn’t pull him out (as according to their plans to correct the “omniverse”).
So, he’s stuck here, and the only option is to use the machine again. He’s going to need to find the Observer. He’s going to need to convince him he needs to go back to that day on the ice, and pull him out. And, while the Observer will be reluctant, he’ll do it because he’s obviously emotionally compromised in his “mission”. And this will bring everything full circle… and we’re back where we started, because the universe Peter finds himself in is the one that was supposed to exist.
The universes from the previous 3 seasons were ones where the Observer interfered in saving the life of Peter. But why? Because Peter convinced him to.
So, now that I wrote all that out, I can’t wait to see how way off I am. This show is fun.