It is somewhat of a problem: the development team is very small, they don't take outside contributions (so nobody outside the core team really builds up expertise over time), and the vast majority of tests are proprietary. I hope they have a contingency plan just in case (some sort of a dead man's switch that publishes the test suite under a permissible license) as it would probably be quite difficult for others to maintain the same quality without those tests, or re-implement them in a reasonable time frame.