As I mentioned earlier, the regulation does not define "extraordinary circumstances". This has been left to the courts which have offered varying interpretations. Only now is the interpretation before the highest European court.
When the regulation was being drafted everyone, the Commussion; the Parliament; and the airlines were all in agreement that nothing in the regulation should compromise flight safety. I.e. An airline should not be encouraged to operate even a little unsafely, to avoid a significant compensation claim. Particularly when the compensation amount has no relation to the fare paid.
An airline with a 189 seat aircraf operating an intra-EU sectort could be liable for €47,000, a long haul 777-300ER with 458 seats sees almost €275,000. For many flights these compensation amounts exceeds significantly the fares paid. And in many cases it isn't a single flight that would be delayed, but a series of flights.
So lacking a clear and consistent definition of extraordinary circumstances I can fully understand why some airlines are waiting to see the ECJs final interpretation. I personally doubt that the ECJ's ruling will please them but they are not acting inappropriately by waiting for it.