Copying comments from planning:
Per Ramesh, the suggestion/proposal (we talked about this couple times) is to keep a DDL version of the Model along with the XMI model in separate tab in the Designer and let users check in the DDL version into the SVN/GIT using "team" feature in the Eclipse. Since DDL file will be text based, the merge and diff are facilities provided through Eclipse tools. We need to use the team import feature to update the XMI model when reading from SVN/GIT. This will give us closest collaboration platform we are looking for without waiting for Komodo and I believe it is fairly achievable goal.
The initial import/export (generate) features for dynamic vdbs perform the needed operations. Now that we have both *.vdb and -vdb.xml resources we can think more about how to assist the user. CSV/GIT in Eclipse is certainly an attractive option. Linking a -vdb.xml file to a *.vdb and auto-saving both is also an option. And as Van said, differencing via CSV/GIT would be the direction I'd vote for.