lol. Nintendo makes billions on hardware and software. Dumping the hardware would just mean less profit overall. Nintendo themselves have said that the day they stop making consoles is the day they stop making software.
There is a good reason you want to be in control of the hardware. Nintendo knew that they were adding motion controls and IR support to the Wii, and they made games that took advantage of it. They can build software to the hardware's strength, and build the hardware to make the types of games they wish to. Nintendo made the Wii so they could make games like Wario Ware, Mario Kart, and other games that support motion control.
In the end, if your console is winning, who cares if you get 3rd party support. Nintendo isn't stopping them from making games, 3rd parties just choose not to. Nintendo wants 3rd parties to make games because it means more money for them and more interest in their console, but they don't have to worry about 3rd parties.
How does supposedly going from 3rd parties not competing to having to compete with everyone on another console benefit the software side of their business?