Has sly 4 already bin realest

No.But it will be released July 2008.
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That answer is fallacious. The company who made the Sly series is still working on another project on the PlayStation 3. The game that they are working on is so far being called Infamous. For now Sly 4 has not yet been released and no, it is not going to be called Sly 4: King of Thieves. This is what has rumored to be called but is not necessarily true, unless of course Sucker Punch Productions (the company who made the Sly series) decides to use this.