Well, you can probably use Project Spark or the C++ to make indie games for Xbox 360, Xbox One and Windows 8. But then, it may seem that Project Spark is something like Kodu Game Lab which may be way too simple when it comes to creating games with that. I don't know what to say about Kodu Game Lab when I discovered and tried it the last time. There may be similar games such as Minecraft or Little Big Planet in which Project Spark is going to be something like that where you can make custom levels with supported kinds of gameplays you want.
The previous announcement from Microsoft is the ID@Xbox program that will support self-publishing of the indie games. Previously, there wasn't Kinect support at all and the Xbox 360 Indie developers didn't have access to Xbox Live. I don't know the release date for this program but I can assume that it was already released.
