GeoMFilms said:

When the Emperor talks to Vader about the pilot that destroyed the death star it was like the cat was out of the hat. Now Vader had to lie to the Emperor.

Remember this conversation only plays out like this in the recent SE versions, the conversation in Ady's version will be as in the theatrical version (with a few tweaks, due to the manipulation of Ian McDiarmid's lines)

My take on the original Emperor and Vader conversation makes me believe that the two had previously spoke about Luke Skywalker, his part in the destruction of the Death Star, that he was the son of Anakin and they knew he was rising in ranks in the Rebellion, but when Palpatine states 'we have a new enemy' he refers to the Tremor in the Force that is emitting from Dagobah...A Jedi Master has returned and young Skywalker is about to begin his training

If you watch the film with this in mind, it makes the new conversation shallow