This is an idea which had occurred to me when Disaster was pushed back to early '09. Nintendo dropped a lot of major titles early in '08, and they've all sold amazingly without any holiday boost while keeping the Wii software release schedule looking lively during a period where new releases can be weak.
In other words, Nintendo has no need of a holiday boost for their first party releases. They know that Brawl, Kart and Wii Fit will move plenty of units this December anyway. They're deliberately leaving their holiday lineup weak so that third parties can get a nice big boost and prove that the waters in the blue ocean are fine.
Disaster has been in the works since at least 2006 and shouldn't be very far from completion unless some serious development snags have come up. But it's also the least "Nintendo" of Big N's upcoming titles, and the most likely to directly compete with hardcore third party games. Kirby Wii was also supposed to be on the menu this year, and nothing has been seen of it.
So yes, I think this might be a deliberate strategy on Nintendo's part to slay one of the Wii's last percieved problems.
Or maybe they really did hit a lot of development snags. It's not like Nintendo is afraid to push back release dates when a product isn't ready.
"The worst part about these reviews is they are [subjective]--and their scores often depend on how drunk you got the media at a Street Fighter event." — Mona Hamilton, Capcom Senior VP of Marketing
*Image indefinitely borrowed from BrainBoxLtd without his consent.