* The Wii is discontinued: Nintendo discontinued the Wii console in 2013. While some people still play it, it's no longer being actively supported for new games.
* The Monkees aren't actively making new games: While The Monkees are still touring and releasing music, they haven't been involved in video game development in recent years.
* Licensing and development costs: Developing a new video game is expensive, and licensing the Monkees' name and likeness would add to the cost.
While a new Monkees Wii game is highly unlikely, it's not entirely impossible:
* A fan-made project: Some fans might create a non-commercial Monkees game for the Wii.
* Re-release of an old game: A previously released Monkees game for another platform could potentially be ported to the Wii.
However, it's safe to say that a new, officially licensed Monkees game for the Wii is not in the works.