Yeah, Nintendo games have great legs in Japan. Everyone has to remember that the majority of NSMB sales came from the months after it's launch, where it averaged about 20,000 - 30,000 every week. Even though it easily sold over 1 million in it's first month, the other 3.5 million copies came from the next year's worth of sales.
Even the article says the 130,000 it's first day is better then Mario Party 8 first day sales. The last time I checked Mario Party 8 had sold over 800,000 copies in Japan. So if Galaxy is already off to a better start then Party was, I'd imagine it should be able to sell around the same amount if not more.
Oh it should also be stated that Super Paper Mario sold over 400,000 copies in Japan, and since the Mario RPG's are less popular then the main Platforming one, Galaxy will do a lot better then that. Hell even Twilight Princess was able to pass the 500,000 mark in Japan and we all know that Mario is more popular then Zelda over there so Galaxy will at the very least be over 600,000.