At the beginning of 2010 the Wii will have a 30 Million unit lead on the PS3 and will be outselling it worldwide on a monthly basis, and there is little reason to believe that the PS3 will be able to overtake the sales of the Wii by a wide margin in 2010; so it is safe to assume that the Wii will have at least a 30 Million unit lead on the PS3 at the end of 2010.
Now, regardless of what console manufacturers claim, it isn't realistic to expect these consoles to have not been replaced by their manufacturers much past 2012; and it is not realistic to expect much in the way of sales from any of these consoles much past 2013. This gives the PS3 (at best) 3 years of sales to make up for a 30 million unit lead when the PS3 has averaged less than 10 Million units sold per year since it launched.
Basically, even if Nintendo stopped selling the Wii at the end of 2010 and Sony was able to sustain sales of the PS3 through 2013 the PS3 still couldn't pass the Wii in lifetime sales.
I think that it is possible that the PS3 could achieve sustained sales above the Wii if Nintendo releases a new system in 2011; but the PS3 would never be able to have the kind of sales dominance over the Wii that the Wii had over the PS3, and the beginning of a new generation would soon end the lives of all three consoles. When you combine this all together, the PS3 is never going to catch the Wii and probably doomed to be third for the rest of the generation.