Question: It is clear that Rava did not become the Rosh Yeshivah until after the death of Abaye, as is evident from the episode with bar- Hedya cited earlier (56.).

Proof: And similarly in Kesuvos - where the Gemara (at the end of Perek Af-al-Pi, Daf 65.) relates how Chomah, Abaye's former wife, came before Rava.

Question (cont.): The question now is from the Gemara earlier (on Daf 56.) which implies that Rava dreamt about his wife's death before Abaye died?

Answer: Nevertheless, she did only died after Abaye.