I'm gonna have to say I still think DS will see a price drop this year. It's no longer supply constrained, and Nintendo has put a significant investment into increasing production and shipments. Unless they contracted for a very temporary increase in production, they're going to want more than just for sales to hold steady.
Sure, they're guaranteed a fantastic holiday this year, and they're doing very good in hardware and software, but a drop to the magic $99 price point (or the Japanese equivalent, 10,000Y?) could help push a lot of older software this holiday season (stuff like Kirby SS, YIDS, Love & Berry and the like). At least in Japan and the US, a pricedrop around about September makes sense, along with the introduction of the first 'Player's Choice' line of DS titles. That'll put a lot of DS's, well okay a lot more DS's, into people's hands shortly before DQIX releases (and Zelda PH in the US). I'm not sure on Europe, DS seems to be selling ridiculously well there, as it is in Japan, but I'm not sure if there are shortages or not.
As for the Wii, if it keeps up what it's doing (and the release schedule for the rest of this year pretty much seems to guarantee it will) it may go longer than the 360 without an official price drop.
Edit: Muddled Greatest Hits & Player's Choice into some weird amalgam of terror. Fixed now.