The only thing that could "save" the Wii U at this point is what "saved" the PS3: a massive price drop and a willingness on Nintendo's part to bleed enormous amounts of money.
If Nintendo is willing to drop the price of the Wii U to 150 bucks and lose 5+ Billion dollars on the Wii U as Sony did on the PS3, I can see that having a dramatic effect on sales.
Barring that extremely unlikely scenario, I don't see any method for the Wii U to be any more than a marginal, niche product.
Going for 350 to 150 buck would be financially brutal however I don't think Nintendo can avoid dropping the price to 250 $/ in the West and between 20-25k yen in Japan + doing bundles (worldwide).