Interesting question. One possible solution imo, is too keep the "Wii" brand not anymore bounded to a console but to the controller style. For example Microsoft lately is using 2 brands at the same: time the "X360" brand for the console and "Kinect" brand related to certain games and to the control style. In a similar way Nintendo could use "Steam/Cafè" brand for the new console, while keeping the "Wii" brand for the Wiimote/nunchuk gameplay style, and the relative compatible games. Yes this may cause some confusion in the begginning but after all, it's the same thing happening with DS and 3DS. Another option may simply be to put the "HD" brand in Wii games and simply call them WiiSports HD.
However it's a little too soon to start talking about this, as far as we know from official news the N6 may still keep the "Wii" brand in its name, like "Wii Steam", "Wii2" etc. etc.
As for casual and harcore gamers, they can coexist without problems, the only important thing are games. Casuals and Hardcore already coexisted on Ps2, the only difference is that, at the time, we weren't discriminating.
