I doubt its going to be that much more expensive.
Kinect 2.0 will invariably cost more, but I don't see it adding more than $100 to the cost of the console. Given that they're going to probably push subscriptions as a way of subsidizing cost, it'd be stupid of Microsoft to charge anything above $399 for the console - I think they launch it for $299, pushing a 2yr subscription, with the console costing ~$500 to produce.
Back from the dead, I'm afraid.







