The ideal outcome would be a common shared office-XML dialect for the
basics—and it should be ODF (or a subset), since that’s been designed and
debugged—then another extended vocabulary to support Microsoft features ,
whether they’re cool new whizzy features or mouldy old legacy features (XML
Namespaces are designed to support exactly this kind of thing).
That way, if you stayed with the basic stuff you’d never need to worry about
software lock-in; the difference between portable and proprietary would be
crystal-clear.
And, for the basic stuff that everybody uses, there’d be only one set of
tags.
This outcome is technically feasible.
Who could possibly be against it?