Sega has just been hit really hard by the first day sales of Sonic Rush Adventure in Japan. Even with all those DS units floating around in the Japanese public, SRA only managed to move 1,500 units. That is absolutely abysmal for a character like Sonic.
Enterbrain states that Japan has seriously lost interest in Sonic due to a string of less than stellar games. I don’t know that Sega will be claiming 4 million Mario and Sonic units sold for much longer.