В этом 3-минутном интервью Линус объясняет, почему такая стабильность ядра версии 2.6 вызывает задержку при переходе к ядру версии 2.7.

Из интервью:

"One of the original worries was that we would not be able to make big changes within the confines of the development model... I always said that if there is something so fundamental that everything will break then we will start at 2.7 at that point... We have been able to do fairly invasive things even while not actually destabilizing the kernel... Having stable and unstable in parallel: I think it used to be a great model, and I think we may see that the kernel has actually become more mature and stable and it just doesn't seem to be that great a model, for the kernel."