The actor told Entertainment Weekly that it "would be horrible" if his character Walter was killed off.
"I think the fans would storm the citadel," Noble joked. "But I think it would also be really honourable and dignified if they find some way for Walter to willingly end this nonsense. But I don't actually know how they'll do that yet. But I believe they have to."
The 63-year-old star added that he is "not sure" if a heroic death would be a fitting end for the eccentric Walter.
"The storytelling mode, does it work to kill off a hero? I'm not sure that it does sometimes," he suggested.
"You can see a person go through an enormous journey, but somewhere at the end of that journey, there's a change - whatever the change is. It's [usually] a change for the better, even though it may mean that person is not there."
Noble's co-star Anna Torv recently claimed that she would be happy for her character Olivia to die once Fringe comes to an end.
The fifth and final season of Fringe will air on Fox in the US and Sky1 in the UK later this year.