The difference with the PS3 was it had the entire backing of the third party community. Developers couldn't afford to rely only on the XBox 360 and Sony had a lot of built in credibility with third parties after an 11 year stretch of being no.1 with PS1-PS2.
Sony really only had one main problem -- the price, which was going to become less of a factor over time, and ultimately over the course of a 7 year console cycle, it wasn't a big deal for the last 5 years of the gen.
If Nintendo does everything right from here on out, I could see maybe 30 million WW, more if they can conjure up a break out new hit IP but I would say these are extremely optimistic scenarios.
If the Wii U had a chipset that wouldn't be outdated in a couple of years, I would say they have more of a runway to make up for their mistakes, but alas.
