Will AbiWord use OpenDocument as its default export format?
The question is more complicated than it seems but the short answer is unfortunately: No. See this mailing list post for a good summary of why AbiWord is unlikely to ever use that format by default.
Basically, Abiword's default file format (ABW) is a simple serialization of its internal data structures. Converting from/to OpenDocument (or any other format, for that matter) is always subject of error, so it doesn't make much sense to use it as default file format. But it does make sense to have an import/export filter, and Abiword offers that.
Note that you are free to set OpenDocument as your default export file format in your own profile.
Will AbiWord support the Open Document?
Yes. There's currently decent import support for OpenDocument. We also recommend Rich Text format as the best way to share documents with other Word Processing software. I would like to read ods files
I still want to make it default!
Same as for setting the default to MS-Word format, but using .odt as the extension.