Once a game disc has been loaded into the console with an update on it, there will be a notification streaming across the Disc Channel (the new channels that are coming for Mario Kart and WiiFit, for example?), much like how the Wii Shop Channel now streams release information for Virtual Console games. And the update improves the system’s performance overall. Which is always a good thing.
If your Wii is connected to the Internet, you should be receiving a message from Nintendo shortly instructing you on how to update. If you haven’t received the message go to Settings, System Settings and then go to the 3rd Page and choose “Check Online for Update”.
The update has not fixed the exploit found in the Wii that we first broke on December 28th, 2007, “Wii Officially Hacked” The Twilight Princess hack still works and all homebrew is still working (Pong, Tetris, etc…).
So, if you were concerned about that, no worries.