Nintendo's pretty good about taking care of what they already have. At the very least, they're doing a better job than, say, Sega, so they don't have much to worry about. They have a lot of sure-sells in the big names, so they can afford to keep things hush-hush.
I kind of prefer it that way. Hearing about a game -too- long before it actually comes out just leads fans to spend all that time speculating. And then they blow it out of proportion and tend to be disappointed that the final product isn't exactly what they've spend the past year(s) dreaming it to be.
Nintendo is just way too big to honestly fail. Consoles appear to be gimmick-y at first, but eventually turn out to be pretty decent machines. The sure-sell franchises keep a cash flow coming in, and their practice of not releasing too much about their plans at once usually pays off by making us check back with them often for news. They are the only company I do that with. All the others talk so much hype about their stuff, I don't have to worry about missing a particular bit of news because I'll probably hear it three more times between now and release.