I think that Nintendo tried out AC GCN for the American audiences to see how they would react, and the reaction was phenomenal. Now, Nintendo wants to see what happens with AC DS. If that is huge, then Nintendo will focus on the AC franchise more. AC is huge in Japan, but not, of course, like Zelda. AC is a new-comer compared to Zelda, so AC needs to respect its elders, Mario and Zelda.
But seriously, if AC DS is succesful, then AC Rev will be HUGE.