We mucky commoners have known about the Wii MotionPlus add-on for just over a week now, but don't go thinking it's any different for third-party developers. At E3, Game Informer approached several third-parties about the peripheral, and were repeatedly told that the accessory was news to them -- as they understood it, Nintendo simply hadn't told anybody about the MotionPlus, prior to it being revealed last Monday.
In other words, we can safely not expect a flood of third-party releases supporting the peripheral. On top of that, the developers doubt they'll be able to implement Wii MotionPlus into upcoming projects, such was the secrecy that surrounded the project. Not clever, Nintendo.
Nintendo Wii Remote controller