Be careful current and soon to be Wii U owners. The console being shut down during initial update can brick the console.

[the_dengle]

Barozi said:
Is the automatic shutdown activated by default ? If so when does it shut down ?

The console automatically turns off after an hour of inactivity -- this can be disabled in system settings, but it's been confirmed that this function is INACTIVE during the system update. The console will NOT turn itself off while updating.