Revealed by the platform holder via Twitter, the optional download is being rolled out to improve software stability.
"PS3 system software update 4.21 will be released soon. It's a minor, optional update that improves software stability," Sony wrote.
The news follows reports that Sony's PS Vita handheld console is to receive firmware update 1.8, a patch that will allow users to download and play PSone titles on the platform.
Earlier today, leaked documents suggested that the gaming giant is working on the ultra-slim PS3 4000 series, which could be unveiled at gamescom in Germany next month.
An official release date for software update 4.21 is yet to be confirmed.
