Most of us that are thinking about the future of a joint system...realize the limitations and the trade offs...which is why we don't see this happening next year. Probably not next console generation...but it could happen in 5-10 years.
Look at the level of graphics being achieved NOW by the Vita and tablets of the world. Yes, those machines are not cheap...but they could be a heck of a lot cheaper in 5-6 years. In 10 years we could definitely create games at standards that gamers will expect and developers can afford for a portable/console hybrid...and it wouldn't have to break the back to buy.
Honestly, Nintendo would just need to keep in it in the $249.99 price point. Since it is also doubling as a console system. Then Nintendo could have a package that is 199.99 without the TV hookups if gamers desired. A later purchase could include such features.
I like the idea of a charging pad, console docking system that houses the components to hookup to the TV, have additional USB ports for hard drives, and even 4 ports to charge 4 controllers.