According to my calculations (which, in all likeliness, could be wrong), the PS3 has sold at a 28.5% market-share since the launch of the start of September (well, week ending 29th Aug) in the Americas.

On the week ending the 21st November, its weekly market-share was 22.6%

The PS3's current overall market-share in Americas is 18.6%, on the week ending 29th August, it was 17.7%, meaning that it has gained 0.9% since the launch of the slim, 12 weeks, we have 5 more weeks of data to come before Christmas day.

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Based on these figures, I'm going to predict that the PS3 will hit 20% market-share at the end of January.

probably never

but lets see

Hm...

It really depends how the Christmas boost works.

Whether or not it's proportional and if it's enhanced or decreased from baseline due to the pricecut.

The sales increase that is.  Not actual sales.

It could reach 20% by second quarter 2010

If it doesn't hit it by summer of 2010, it'll probably never get there.