The Fox sci-fi drama - starring Anna Torv and Joshua Jackson - was officially picked up for a final 13-part run last month.
In a recent conference call, Jeff Pinkner and Joel Wyman appeared to deny that the new season would take place in the future world first glimpsed in recent episode 'Letters of Transit'.
"That future is important to our storytelling," said Pinkner. "But it's not the be-all and end-all."
The pair also refused to rule out a comeback for Leonard Nimoy as William Bell, after the character was briefly glimpsed in the future-set instalment.
Pinkner joked: "We basically erected a sign outside of Leonard's house that says, 'Please come back to Fringe' - we are hoping that by season five, he says yes."
The showrunner also remained cagey on the future of cast member Seth Gabel (Lincoln Lee), who returned to the alternate universe in 'Worlds Apart'.
"Seth is spectacular and awesome," said Pinkner. "But as for his standing going forward... to say anything about that would be also to reveal things that are coming ahead."
Discussing the upcoming season four finale, co-exec Wyman denied Fringe star John Noble's claim that two potential endings had been filmed.
"We did not shoot an alternate ending," he insisted. "We thought about it, but we did not [film it]."
Fringe continues on Fridays at 9/8c on Fox. In the UK, the series airs on Tuesdays at 10pm on Sky1.