Twitter user Wario64 spotted a listing for Red Dead Revolver on Australia's PlayStation Store (via GameSpot). The listing had a release date of tomorrow, September 13, and a price of approximately USD$17.
The listing disappeared as quickly as it popped up. Neither Sony nor Rockstar has mentioned it, or made an official announcement that a release is incoming. Whether a release happens tomorrow or at some other point in the future, it would be a PS2-on-PS4 port rather than a full-blown remake.
Released in 2004, Red Dead Revolver marked the start of Rockstar's Red Dead series. The most recent entry, Red Dead Redemption, was released in 2010, and has been the subject of sequel rumors for the last several years.