Nintendo won't drop the Wii U, they make money off their hardware. Compared to MS & Sony who sell at a loss.
Xbox has yet to turn a profit for MS. Sony's gaming division hasn't made money in years.

It won't print Wii money, but it'll turn a pretty profit.

Oh and re: the Dreamcast, it didn't kill Sega, it just wasn't successful enough to save them from years of costly blunders (32x/CD/Saturn).