Syphon Filter 3's arrival in the PS Plus Classics Catalogue was always a when and not if after Sony earler added the first two games in the series. But, it appears that Bend Studio's third-person shooter is coming to the PS4 and the PS5 sooner rather than later.
points out that Korea's Game Rating and Administration Committee has classified the PS4 and PS5 versions of Syphon Filter 3. The listing all but confirms that Syphon Filter 3 is one of the next games headed to the PS Plus Classics Catalogue, which is reserved for the highest tier of Sony's revamped PS Plus service.
Many speculated that Syphon Filter 3 will join the Classic Games lineup on November 6 on its 21st anniversary, but this hasn't happened yet. However, the listing suggests it's only a matter of time before Sony makes a formal announcement, possibly in a week or two as it releases the list of new games coming to PS Plus Extra and Premium/Deluxe.