Don't expect a complete overall/revolution on the dashboard side, as i said on a previous thread, it's a natural evolution of the Wii "channels" organization, with improvements, some of them deriving from the 3DS.
It will be efficient and well-thought.
About Miiverse, there's a possibility it won't be available at launch, considering third-parties can't access it right now.
It really looks like the Wii U will be a multiple stage rocket. To avoid customers being overwhelmed by the plethora of features, keep some ammo against the competition and inject additional momentum during its lifespan, they will have first the system itself and the gamepad, then Miiverse, then the NFC, the two gamepad's, etc.
A nice move imo