They can reach those kind of sales if they play their cards right.
If they streamline their games production that will not only allow them to fully support their consoles - with even a game per month! - but they will also need new franchises to fully support the consoles throughout their lifetime. Which could and should mean new franchises like Halo, Gears of War, Uncharted, Gran Turismo, Demon's Souls, etc.
With the extra staff they can develop bigger projects and more ambitious projects.
Another factor that could also help sales of the console is if Nintendo bundles the home console (just the console itself) with the handheld, for 350-400€/$.
That would really attract a lot of customers because of it's incredible value.
Also, if Nintendo follows the above path, a special retribution system for game purchases for those who own both consoles, would be a very good incentive for people to buy both.
