There wouldn't be much point in the Natha dedicating valuable time and resources to preserving their bodies if there was no possibility of them awakening.

[It's less optimism in Mephisto's mind and more like common sense. The Natha didn't strike him as the sort to be sentimental -- though he has considered that some of those still asleep might just be preserved for the sake of making those who did survive more compliant.]

Still, I wonder if it wouldn't be wise to ask the Natha just how much time passed between our own awakenings and the destruction of Assiah... I doubt so many worlds were taken out all at once. We could have very well been in stasis for years, if not longer.