North American users are urged to wrap up any pressing purchases through the digital storefront before 4 p.m. EST. Nintendo of Europe's tweet states the European eShop will be closed from 10 p.m. CET to 10 a.m., which almost sounds like enough time for it to ... sleep. Oh no it's developing human-like needs
Nintendo will have "more updates soon" concerning the NA eShop's status, presumably involving when users can expect it to reopen its imaginary doors.
Update: Nintendo's Online Service Status page lists the planned network outage from 4 p.m. to 4 a.m. specifically for the 3DS eShop. This is reflected in attempts to access the 3DS eShop itself, which result in an error explaining the temporary downtime. However, we're also currently experiencing problems connecting to the North American Wii U eShop. Several attempts to connect have all resulted in the initial eShop loading screen fading into a white screen that goes nowhere, though the home menu can still be accessed from this state.