The Wii definitely isn't down on its luck, as we've seen with its success in the market. Unfortunately for the customer, Nintendo has been having difficulty in keeping store shelves stocked with the console. According to some analysts, this trend will continue – demand for the Wii will remain high while supply will remain low:

“I believe the Wii will continue strong growth although supply continues to be a problem,” said Billy Pidgeon, video game analyst, IDC. “I’d like to see Wii hardware shipping in larger quantities or mass market consumers may cool on it. Having said that, I don’t believe supply will meet demand for the Wii until 2009.”
On top of that, many are still predicting the PS2 will continue to thrive, well above the PS3. Particularly due to a lack of selection on the PS3 and Xbox 360 and lack of interest in hi-def consoles, the older console has a lot going for it (aside from price). On the Wii side, Nintendo hasn't mentioned if they plan to expand manufacturing, though it would clearly be to their benefit. If sales do continue to perform as they have for the next year and a half, the Wii wll have ascended far beyond Sony's claim of it being an “impulse buy”.