According to long-standing online Nintendo leak sources, the Wii will ship with a system updater disc when it goes on sale in the coming months. The content of the disc - referred to internally at Nintendo as Wii Start-Up Disc - is unknown, though it is speculated that a firmware update is required for the first batch of Wii hardware already waiting to go on sale.
As you will have read, Nintendo has recently dropped hints that it's well underway with Wii production
a direct reaction to Sony's well-publicised issues with PlayStation 3 manufacture.
Further speculation outlines the Wii online beta test will take place between September 18 and October 23 and will seek to bottom out all bugs in the Wii's Virtual Console, WiiConnect24 and 'other' online elements. Some assert that this test essentially dates the console for an October 23 launch, though as you know, an online service can launch well after its host hardware.
It's also worth pointing out that Nintendo has already let slip the fact that any online offering the Wii will have over launch will be scant at best, with third-parties complaining that they are unable to provide 'Net play on day one.
At time of going to press, it is unknown if any Nintendo first-party titles will make use of the Wii's access to Nintendo's online services.