Some people are mentioning that the firmware is being pushed to address issues with the connectivity between the PS3 and Vita. Who knows for sure? The update is for US and Canada consoles only, both regions in which the Vita was released today.
Click here to visit the download page for the new firmware from a PC. Works if you live in Canada as well.
UPDATE: The PS3 Firmware is now live throughout the world, and is now mandatory to update. That was a short amount of time if you ask me.