First if 360 or PS3 catch up (or at least begin to catch up) on market share as dominant console. (IE: Their motion controls or some other reason cause them to sell...) More likely, it will be the last not the first.
$300 is possible as a worse case, given inflation, etc... and as a way to milk early adopters. However they will be able to lower the price quickly if needed and they start that high.
I am sure they will be able to make it for under $200 and have better cpu and graphics than the 360 and ps3 by the time they launch...








