It's not Nintendo who has to fill the gap on Wii, it's the third parties...
They were very slow at start, but just like with DS in its third and fourth year, they now can see Wii is a market leader, with a huge userbase, and last but not least, excellent profit margins...
Next step is to realize that just as DS, all kind of games may find their public on the console: not only platformers-puzzle-casual sports, but also RPGs, FPS, mature action, survival horror, and all the genres usually associated with core gamers...
We can see the first very good signs this year, but 2009/2010 will be the most important years in Wii's life, with way more "real" efforts by third parties, plus the usual Nintendo's 1st party greatness: it will be a nice mix, and just like with DS, i think Wii will have something for everyone, and way more 80+ and 90+ games...
So yes, Nintendo's future looks quite good, and the most dedicated third parties will also have a slice of that huge pie, whether it's on DS and/or Wii...
Of course, Nintendo is now so rich they could also buy some smaller devs to create more 2nd party games, especially mature core games, just the way they did with Retro or Monolith...
But i think they will not spend their money that way, they will instead make more and more deals with third parties to give them support and assistance, offer them unexpensive dev tools, publishing and promotion deals, to create good quality exclusive titles hand in hand... think Sega with the Mario and Sonic, Tecmo/Grasshopper with Fatal Frame 4, Rockstar with the future GTA's... you've got the idea...

"A beautiful drawing in 480i will stay beautiful forever...
and an ugly drawing in 1080p will stay ugly forever..."







