I don't get how backward compatibility on the wiiu is restricting the future in any way. The thing can use most (if not all) of the controllers and gimmicks of the wii, thus prolonging their lifespan. The wiiu is not very different in structure, so I doubt adding backward compatibility was much of a cost for nintendo. Or for the consumers.
I don't think developers care much about it either. Regular wii games may drop in price drastically, but I don't think that is stopping anyone, as the graphics are vastly superior now. And on the flip side: if people buy a cheap game from last generation and like it, they are more prone to buying the sequel/next entry in the franchise on the new platform.
For other consoles...the way I understand it, they are built with different hardware, making it harder to provide backwards compatibility (the earlier PS3's were more expensive because they had additional hardware that was needed for PS2 games). So I can understand why sony and microsoft don't provide it (heck...nintendo has to break compatibility as well at some point).