I spoke to David Mitchie (creator of SWISH and openswf.org) some time ago. He told me that the FLA-format could never become an open format. The reason for this is that the FLA is simply a memory-dump from the FLash application so Flash is the only app that can read it back.
The only effort made in this direction was OpenLGX (http://www.openlgx.org/) and their LGX format. They gained support of many major players, but have now been sued by "the big boys" and is probably out of the business... Really sad actually. These guys had a really good thing going.