There will be a lot more than 10 million consoles sold in the next 4 months, theprof. Historically, roughly half of all sales for a console in a given year happen between September and December. This year's grand total through August is a combined 23.68mil consoles sold between Wii, PS3, and 360. We'll likely see about as many more consoles sold between now and the end of the year.
In that light, they actually only need to sell about 58.5% of those 23.68 million systems to hit 50% by the end of the year.