Another system update is already available for the Wii U. While Nintendo hasn't specified exactly what the update will include – though we're anyone who owns one of the consoles will be hoping for something to magically shorten loading times – it has given details on how long the update will take.
If you already sat through the first system update that will have to be performed on all Wii Us (whose owners want to take them online) bought before an as-of-yet unspecified date in early 2013 when it'll be included in new consoles, you'll be able to carry on playing while the update downloads, and even turn your console off (though don't unplug it). As long as your Wii U is connected to the internet, it'll download the update in the background. It might still take up to an hour to download, but at least you can get on with watching Netflix as it does so, maybe occasionally checking in via the Download Manager.
Those who haven't yet updated their Wii Us with the initial, day-one update will have to find something else to do while the update downloads and installs, which – again – could take an hour or so. Nintendo also points out that the progress bar that displays on the GamePad during the update might take a while to start moving, and this is apparently normal. So, don't panic, I guess!