Nintendo really can't do anything until next-generation (Wii 2). They are building a huge new R&D facility next door to their current one (they purchased the land last year) in Kyoto, but it's going to take a couple of years to build the building and staff it up and get going on projects.
The DS is a different story because it has the full backing of the Japanese 3rd party community (ahem Square-Enix for starters) because it was the successor to the GBA, so it got every benefit of the doubt from devs, whereas the Wii being the successor to the GameCube has gotten none. That has led to a chain reaction where devs have scrambled to get Wii software out, only to release sub-par software, which inevitably bombs, and now they're confused about the Wii. Third parties honestly probably will need a clean slate too -- with Wii 2.
It doesn't hurt that in North America and Europe, the PSP is basically a walking dead platform ... it really fizzled out here around 2007 or so. I do think btw that DS sales would be down this year, but the introduction of the DSi model is buoying DS sales. If you'll recall in 2008, the DS was down year-over-year big time in Japan until Nintendo introduced the DSi. The Wii does not have this luxury (though I'd gladly buy a Wii HD if Nintendo made it).
On the positive at least there's this ... because of alligning dev cycles, November 2009-November 2010 might be the best console year in Nintendo history.
You are looking at New Super Mario Bros. Wii, Sin & Punishment 2, Super Mario Galaxy 2, Metroid: Other M, and possibly a new Zelda and/or a new project from Retro Studios on top of slated games like Dynamic Slash, Span Smasher, and Monado which could also turn out to be decent. Enjoy it, because you may not see another 12 month period like that for a while.