There is no set formula for figuring out which console will be the most popular. Secondly, price cuts will attract new people, but they will also attract the people that have been wanting to get a PS3 or whatever for a while, but haven't because the cost was prohibitive.
The only "formula" that I would reccomend using, would be the entirely subjective Value/Cost ratio. The PS3/360/wii is worth more to some than others given their income, spending power, like or dislike of the console system, etc and the console companies are always trying to make that ratio go higher, hence we have online gaming and a lot more things going on than 10 years ago. That is also why you will frequently see price-cuts for mass-produced products, so that companies can gain market share, and hopefully choke off the competition.
To awnser your question more directly, all else equal, a decrease in price of a product will increase the quantity demanded of that same product. Of course, price isn't the only thing going on with any market, so a more comprehensive analysis should be undertaken than just looking at the whole thing on a price basis.
