Welcome back.
It looks like the Wii has already peaked, true. But you better never underestimate Nintendo. If I were Big N, I wouldn't care THAT much about the Wii right now to be honest. They have a great line up with Wii Party, DKC, Zelda and Kirby. Those four games will easily sell 20 million copies. Dragon Quest on the Wii in Japan will be sick.
But I think they are really concentrating on the 3DS right now. Internal development must be heavily focused on this new device. Make sure you have an awesome launch line-up and the 1 or 2 years after released are filled with great titles. That is their main task right now.
I don't think both HD systems will outsell the Wii. They will eat in each other sales way too much.
Imagine not having GamePass on your console...