Peter is in the future.
Now an adult, Olivia's niece Ella has become a Fringe agent.
The Fringe Division is as prominent on our side in the future as it was in the other universe in present day.
The disintigration of the earth has been caused by Walter, and everyone knows it, but Peter still needs him to help solve the problems of the future.
While Peter interacts with a hologram of Walternate, Walternate shoots Olivia between the eyes.
Olivia receives a viking funeral as her casket is lit afire and set to sea.
After the disaster that was 15 years in the future, Walter realizes how to fix the past.
Peter goes back in time, and saves the worlds.