The announcement post on PlayStation’s US site said:
I’m posting this message to inform you that there will be a minor firmware update (v.4.31) released on the evening of Monday, October 29th.
There will not be PlayStation Network maintenance during this time; online play and access to apps will not be affected during the release of this update.
This is not a mandatory update. However, we suggest you keep your systems updated with the latest firmware, as these updates further improve overall system stability and help provide you with the best online entertainment experience possible.
The last firmware update for PS3 enabled visibility of Trophies earned on Vita on the PS3.