AFAIK ... since Microsoft axed the XNA program and related SDK tools, an
Xbox LIVE Indie Games membership
is currently required at US$99 per year. Also (AFAIK) both Indie Games and Live Arcade brands, are being axed
later in the year, possibly to coincide with the general release of the Xbox ONE, and downloadable games from
indie developers are to made available within a new version of the Xbox Live Marketplace, which I believe
would most likely be available to existing Xbox 360 users as well as those that cough up for the Xbox ONE.
Microsoft said they still want to sell 25 million more Xbox 360 units even after the Xbox ONE is released, so
there's no chance of them dropping it like a stone, and treating it like a 2nd class citizen, as they did with
the Original Xbox gaming system surprisingly soon after the Xbox 360 was released.
Obviously, Microsoft still ultimately want everyone to get the Xbox ONE, but after the recent debacle over
the U-turns related to their highly controversial DRM and other bad PR shenanigans, that seems unlikely.