In the recent third season finale, Peter Bishop (Joshua Jackson) created a bridge between the two parallel universes, but moments later was erased from existence.
"We're going to be able to have people Over Here that are from Over There, [and] we're going to have people Over There from Over Here," Pinkner told HitFix. "There's a tremendous amount of drama. The worlds are still breaking down."
He continued: "What happened to Peter Bishop is obviously a question. Will he return? How is he going to return? In what capacity is he going to return? Fringe has the ability to not do anything normal."
Pinkner also insisted that issues arising from Peter's disappearance, such as the fate of his secret baby son, will be resolved in the new season.
"[With regards to] people's concerns for the baby and Walter and Walternate's history, those answers will become clear," he claimed.
Co-producer Joel Wyman added: "We've said it before that we always plot the seasons out a year in advance. We're not going around [doing things] willy-nilly. It's something that we always lay out and we definitely know where we're going and feel like this [situation] is a perfect set-up for season four."
The fourth season of Fringe is expected to premiere in the fall.
> Seth Gabel promoted to Fringe regular