The GTC plugin formats should become the SonarQube supported-by-default format for any/all languages for Unit test execution and Unit and Integration test coverage.
Language plugins should still be able to import the dominant language-specific format and submit those results as part of an analysis. But for languages where there is no standard, GTC formats should become the norm for SonarQube analysis.
I suggest to blacklist the generic coverage plugin on 6.2, and support the same properties (deprecate them, show a warning). New properties proposal: