I'm more worried about Nintendo's present than their future. The amount of money the Wii must've given them will surely see them through any tough times should they experience any.
But for right now, the majority of games being brought out on the Wii are casual, party games. There are hardly any games on the Wii I'm interested in other than Nintendo's own franchises. I've barely played on the Wii since the first year I got it. When it came out I was all about ExciteTrucks, Twilight Princess, Mario Strikers... a few more games breathed some more life into it - Mario Galaxy, Metroid Prime 3, MarioKart, Smash Bros. Nintendo games have always been my reason for sticking with the company because they are just better than any other games but I still want some decent 3rd party software.
A lot of people say the Gamecube had bad 3rd party support and maybe they're right... but I can think of loads of 3rd party games I played and loved on the gamecube but barely any on the wii. It's the main reason why I bought a 360. I've played on the xbox360 so much more than the Wii.
I'll probably always get Nintendo consoles just for the main franchises that I can't go without - Zelda, Mario, Metroid etc. However, in many ways Nintendo are still a generation behind. Online is a joke compared to 360 or even PS3 now and credible 3rd party games are a lot rarer on the Wii than any of it's predecessors or rivals. For their next console I really want to see proper online functionality as seen on the 360 and decent 3rd party games (though I know that's mainly the fault of lazy developers or w/e).
I thought I was finishing but I just thought of this last point. When the Wii came out I thought the controls were going to be 1:1 from the start and possibly this is why it hasn't done so well with the fps market. I was expecting the motion controls to make me want to buy multiformat games on the Wii rather than anything else but that's just not the case. The controls are more annoying than intuitive... The only game that has used the motion controls really well (in my opinion) is Metroid Prime 3. The controls were that good that I actually bought the trilogy on the Wii just to play Prime 1 & 2 with the wiimote. Any other game on the Wii may as well just use the control pad because the motion controls barely made a difference.
tl:dr wii games suck.
Sorry for this rambling rant. I do this sometimes.