After looking over the current draft of the Atom spec, I think they're definitely on the right track splitting the file format spec from the API spec. In RSS 2.0, the cloud interface is specified within the same document as the file format. While I almost agree that 2.0 is good enough to be frozen as far as the file format goes, it seems to me that many of the limitations of RSS that people complain about could be addressed without changing the file format spec if the cloud API were separated out and it were to continue to evolve.

RSS 2.0 is an evolved and more mature version of the original RSS, but the cloud interface is basically a 1.0 version with room for improvement. I'll post more of my thoughts on this issue later, probably as ideas for an extension to RSS 2.0 to provide a more powerful API than is offered by cloud, on the assumption that those in control of the spec won't be interested in changing it.