The Nintendo of Australia youtube video says the 27th, but it's nearly 4pm on the 27th and it's not here.

It should be today

http://www.nintendo.com.au/index.php?action=news&nid=3493&pageID=6

My guess it will be made live when the American's wake up i.e later on tonight

In the next two hours we get the MK8 update.
http://nintendoeverything.com/mario-kart-8-maintenance-taking-place-tomorrow-likely-for-the-update/

The DLC was slated for tomorrow though, with the eShop update.

http://nintendoeverything.com/mario-kart-8-dlc-officially-announced/

Got it wrong, the DLC comes with the update due in two hours. That's how it's worded in that link.

And the update also brings a shop link to buy both DLC cheap.

Wow, there are people actually care about this dlc! That sure is something

I'm not massively excited for it, but a coin counter and some new rides for free would be nice.

Yep, I want to see if the online is better with the update, and how Daysi looks driving a Mercedes.

My guess would be Friday at the latest, that is when the eshop is updated.