The Scream 4 actor and Cox announced their separation in October 2010, but have insisted that they remain close friends.
Arquette has now explained that it is unclear if he and Cox will ever get back together.
"At some point we'll have to make a decision about stuff, but we're still in the self-discovery process," he told CNN.
"For us, we're very honest with each other. We don't really talk about other people, if we're seeing other people or involved with other people. We're allowed to see other people, but now we're focusing on what our needs are, and if we're compatible as a couple."
Arquette also admitted that his separation from Cox has led him to question whether he ever wants to marry again.
"When we got separated, I had to sort of re-look at all that," he said. "So I don't know about marriage in the future, or other relationships. I know I love love… But you know, having a marriage not work definitely has you step back and re-evaluate stuff. One thing I don't want to do is get back in my marriage or get involved with another person and lose myself again."
Hemlock Drive, starring Arquette and Adam Brody, is expected to be released in 2012.
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Watch the Scream 4 trailer below: