She's definitely leaving after this series, I'm also pretty sure she's not in the Christmas special. Sob. Donna Noble, you shall be horribly missed.

but I don't think Donna dies. Too many hints this episode that she's gonna become Super!Donna - time moving "around her", like Rose said, the fortune teller saying not only "what are you" but the extremely weird "what will you be" and the Doctor pointing out there's too much coincidences around her.... they're doing something with Donna

I think Rose is the one to go to - if she's already back in this reality, there's nothing to stop her from travelling again with the Doctor, which I'm very sure isn't going to happen - there would have to be a damn good explanation (i.e Rose dies) for her not to travel with him again.