What will be considered successful to Rockstar is all that matters.
By the time the game is released, the DS will be at approx. 100 million sold.
All I see is cash from this move.
If 2% - 5% of all DS owners are the "gotta have all games / systems / etc... " there are no problems.
2 million is VERY realistic.
5 million is not out of the realm of possibility.
Either way they will do more then break even, make a huge profit, and rethink their model for Wii as well.
Predictions For Last Full Week of Sales in 2010)
WII - 80.35 Million
360 - 43.88 Million
PS3 - 41.40 Million
More terrible predictions coming Jan. 2011!!!