Nintendo is planning coordinated extended maintenance that'll affect the Wii U and 3DS eShop platforms on 13th March, well after the day's Download Update. What's made us raise our eyebrows to a slightly uncomfortable degree is that this is exactly one month after the last Nintendo Direct, and we know how Nintendo likes to make them a monthly affair.
Random speculation aside, below are the times when disruption is expected on the Wii U and 3DS eShop.
From Thursday, March 13, 2014 1pm Pacific / 4pm Eastern / 8pm UK / 9pm CET to Thursday, March 13, 2014 5pm Pacific / 8pm Eastern / midnight UK (14th March) / 1am CET.
Also of interest for you Pokémon X & Y gamers is that online play and services for the game will be affected for a whopping 14 hours on 11th March for maintenance.
From Monday, March 10, 2014 5pm Pacific / 8pm Eastern / midnight UK / 1am CET to Tuesday, March 11, 2014 7am Pacific / 10am Eastern / 2pm UK / 3pm CET
Online Play, Rankings, etc. for Pokémon X, Pokémon Y