No, its never been stated as canned. Wiki says:
"With the announcement of the PlayStation 4 on 20 February 2013, there was an expectation that Agent may have moved to become an exclusive PlayStation 4 title. However, there was no mention of the game at the launch, but developer Rockstar had signed up to support the PlayStation 4. When asked if Agent was still a PlayStation 3 title after the press conference of the PlayStation 4 reveal during a roundtable media session, Sony Worldwide Studios boss Shuhei Yoshida said "You are asking the wrong person. I have some knowledge, but I'm not in a position to talk about it."
It could be another duke nukem or alien game that spends years in development and being thrown around to other development teams, until someone gets it done.
"I'm not a failure because I didn't win, I'm a failure because I didn't try." - Kev
Youtube: Akirasolid Entertainment