Some years ago, Rational had a dominant position in the UML CASE tools market. As a result, alternative tools had to offer the option of importing the .mdl files generated by Rational (in the same way that word processors have to offer some compatibility with Microsoft Word .doc files) in order to compete with it.
I wonder if the Eclipse MDT/UML2 component can play a similar role now and become de facto XMI standard. Many eclipse-based UML tools use this UML2 component as a native format (and differentiate from the MDT/UML2 component by offering a better graphical editor or more functionalities). A list of compatible tools is available here .
The list also shows two well-known (non-eclipse based) CASE tools (MagicDraw and Rational Software Architect) that also support the import/export of Eclipse UML2 models.
If this trend continues, the number of tools supporting this format may reach a tipping point that forces all vendors to offer some kind of compatibility with this format or face the danger of being abandoned due to their poor interoperability with other tools (an important factor when deciding which tool to adopt).
If this happens we will finally have a standard XMI interchange format, even if it is a de facto standard instead of de jure one we were supposed to have.