A $99 Xbox 360 would affect sales of PS3 more than anything. Gamers unable to afford the Wii U, PS4, and Durango would want to choose between two large game libraries on PS3 and 360. Assuming Sony holds their PS3 price at or about $200 and greater, this would give 360 a dominant share of the last-gen market.
Also, if rumours are true and the new 360 is a backwards compatibility companion to Durango this will also push its sales up as 360 owners switching to Durango would probably be interested in it.
Nevertheless, this will extend the 360 at least another 2-3 years of life. A smart strategy for MS.







