I went ahead and made the necessary changes for this plugin to work with babel 7. I think I managed to get everything working correctly, for both babel 6 and 7, so this should continue work for existing babel 6 users.

Summary of changes:

• babel 7 seems to transform to _exports.default occasionally, so I look for that in addition to exports.default
• getRootPath() doesn't go to the correct root path in babel 7 (which is the error in doesn't work with babel 7 #65). I have modified this to find the correct path for both UMD and everything else
• babel 7 uses @babel/plugin-proposal-export-default-from for the default from syntax. This results in Object.assign(exports, "default", ...), so that needed to be properly detected at the initial traverse. I added CallExpression() which closes resembles your findExportsInCallExpression().
• upgraded tests to test both babel 6 and 7, with the correct env preset and plugins.
• two tests I could not bring over to babel 7, which I have commented on in the tests themselves.
  • should handle duplicated plugin references: babel 7 throws an error on duplicate plugins so this doesn't even run
  • should export with babel-plugin-rewire: babel-plugin-rewire hasn't been upgraded for babel 7 yet, see Babel 7 Support?  speedskater/babel-plugin-rewire#209