The Star Trek actor plays William Bell on the Fox sci-fi drama, which has been renewed for 13 final episodes.
© Fox
"It will depend on what they have in mind for the character," he told SciFiNow. "There are a lot of issues that have to be dealt with, but we'll be talking [about season five]."
Nimoy also hinted that Bell - who last appeared in the show's fourth season finale - could become increasingly unhinged.
"William Bell... started as a very intelligent and rational character," he said. "I think he's still very, very intelligent, but I'm not quite so sure that he's rational anymore."
Fringe will return to Fridays at 9/8c this fall on Fox. In the UK, the series airs on Sky1.
> Anna Torv on Fringe end: 'I'd be happy with heroic death'
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Watch a teaser trailer for the final season of Fringe below:
