The stunning success of the Wii has encouraged Nintendo to open it up to new markets. As such, they are planning to launch the console in two more countries in 2008, China and South Korea. With the current supply barely meeting demand, and no intentions of ramping up production, they have delayed entering into new markets for fear of a supply shortage. After this announcement, we can assume they either expect demand to wane in existing markets next year or for production to increase.
Neck-and-neck with the 360, the Wii has been putting up a tough battle for Nintendo. Opening up two new markets might give them a significant advantage, enough of which that may see the Wii remain on top for the duration of next year. Despite their current successes, however, Nintendo has no plans to implement price cuts or other such tactics to encourage more sales. However, as the cheapest console on the market, they don't need to resort to those tactics.