I can see how bugs are unavoidable, but when bugs are fairly constant are running across different versions without being addressed. That to me is wrong. Part of the reason for new versions should be to be able to address those bugs, if the bug has a fundamental relationship to the previous version. If It doesn't have this relationship, then it should be fixed with a reasonable time frame.
Relating this to Sonar, I think it's reasonable for all inherited reliably reproducible bugs from X3 and before be dealt within the first couple of years, now we don't have a new version structure but a regular release structure.