Microsoft previously announced that every Xbox One console can act as a dev kit. Today at Gamescon, they announced that this feature will not be available at launch. However, Microsoft is planning to give free dev kits for indie devs free of cost.
Xbox VP Marc Whitten explained to Engadget as the following,
“It’s more of a timeframe thing. The vision of how the service and the console work together, how your console can be a dev kit, is a core part of the vision. It’s how we built a ton of the architecture. But moving from a low-scale — a small number of developers — to a large scale, there’s just more work to do there.”