Update: Sony's now confirmed PSN will be in maintenance for North America as well. The PlayStation Store, PlayStation Home and Account Management will inaccessible. The maintenance will start at 9 AM PT / 2 PM PT (12 PM ET / 5 PM ET).
Original: Sony has announced PSN will be under maintenance this upcoming Monday, December 9th for European users.
PS3, PS4 and PS Vita users will experience an eight-hour period of downtime between Monday and Tuesday. The maintenance will start from Monday 9th/Tuesday & 10th Dec between 16:00 and 00:00 GMT.
The following services that will be unavailable during the maintenance are:
Transactions via the console
Users who attempt to signing before the maintenance will be able to remain on their online sessions.