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The sci-fi series and all of its properties - including DVDs, TV shows, merchandise and future films - are worth more than $375m (£225m), according to reports.
"Over the past few weeks, Halcyon and its professionals have engaged in in-depth discussions and negotiations with numerous serious potential buyers, including several major movie studios," Halcyon said.
Halcyon purchased the rights in 2007 for around $25m (£15m).
The short-lived Fox series Terminator: The Sarah Connor Chronicles and recent feature Terminator Salvation, starring Christian Bale, were produced under the Halcyon banner.
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