Who is David speaking to?

I think it implies Mr. Weyland, but as many parts of the movie do the same- It leaves a loophole if needed later. I think there is a bit of genius at work on this film that we are missing in that. The plot "holes" allow for a multitude of directions in the future. A flashback with a new snippet can change the game entirely from what we know now on many parts.

weyland via his dreams whilst in stasis.

Please correct this...Its Mr. John Yutani...not Robert...

Why on earth would it be Yutani? So he can be even more secretive than Weyland, instruct Weylands android, and die off screen without ever being mentioned? Or do we assume that at the end of the film the only things alive on the life boat are the new Xenomorph and Yutani in stasis (where he would not last very long at all in the company of the new arrival).

Let's hope it's not a dream and Shaw wakes up, seeing Holloway having a shower...

I thought Yutani was Charles Bishop Weyland's wife if ALIEN VERSUS PREDATOR: REQUIEM

Are you serious?