We need backward-compatible _applications_, not _formats_!
The idea of a standard format that incorporates a whole raft of older formats is just plain silly.
For years we have had applications, e.g. ApplixWare, AbiWord, OpenOffice.org, that have their own native format but also recognize (automatically or with user direction) various other file formats and deal with them.
In particular, OO.o and its fellow ODF-implementers quite adequately deal with files in various foreign formats, _despite_ the fact that these formats have not been incorporated as part of the ODF standard.
Having multiple formats as part of the same standard might make sense if one wanted to be able to handle documents where each paragraph was in a different format (various versions of MS-Word, WordPerfect, etc), but let's not go there.
If it's true that for most MS file formats and communications protocols the only defining document is the source code of a specific (MS) application, this would go a long way toward explaining why they have come up with the kitchen-sink attempt at a standard that they have. (Speaking of kitchen sinks, how about we have an alternative standard for pipe threads, so plumbers have a choice? Ugh.)