One of the big selling points of descriptive markup is that it is safe. If you use a binary format (or a macro-enabled file) you can have a security problems. I think ODF needs to take a leaf out of OOXML’s book here, and at least adopt the convention where the normal extensions must be opened by conforming applications with macro- and script- and event- disabled. Security is so important, that it should be part of ODF 1.2 rather than a next-generation ODF issue.