Marty from Miiverse has explained on the Wii U social network that the Nintendo Network and Miiverse will be experiencing server maintenance from 4 pm on Monday 30th September to 1 am on Tuesday, October 1st. Whether this has anything to do with the Wii U system update remains to be seen. Yesterday, Nintendo Force writer Emily Rogers stated that the Wii U system update is coming sooner than we think. Fingers crossed, eh?
Thanks, Arnaud and Anubis