Yep. Thanks to the mega-hyped Halo 3 which sold 3.3 million copies, push the sales of the Xbox 360 to 527, 000 units while the Wii (even with the limited availability) manage to push only 501,000 units. So for the first time in 9 months, the Wii's sales figures has fallen to second place.
Not a big deal though, considering the Wii doesn't really have a big enough game to compete against Halo 3 - YET. Mario Galaxy is just around the corner...more details here