The decision isn’t surprising as the company is anxious to put all of its focus on the Wii U going forward. Since the Wii U is backward compatible and able to play Wii titles, there really is no reason to get upset about it. Simply Nintendo determined that it was time to move on.
The Wii had a good run and will live on in the Wii U. The Wii’s software library is pretty vast and while it didn’t have every game you can think of, it does have a lot of games. With Nintendo’s most recent sales success with the Wii U we can see the company putting as much emphasis as possible on the console and discontinuing the manufacturing of the Wii is one way to do that.