The latest Radio Times suggests that Donna and Wilf might be seeing the end. From the quote:
"How much you want the Doctor to triumph, how much you fear for Donna, how much you dread the Master, how much Bernard Cribbins can make you laugh one minute and cry the next. It's all about those wonderful actors, filling your screen and making you care."
"Bernard can break your heart with a look, a gesture, a smile. That's why he;s the perfect companion for the tenth Doctor;s final tale - two wise old men, fighting the good fight. But every soldier must give up the battle in the end, and poor old Wilf has some terrible reckonings to come."
"There were a lot of last scenes for us all," explains Davies. "The last day with poor old Wilf, Donna's final words, the last day on the TARDIS, the last time David used his sonic screwdriver. There was a lot of emotion on set. The most awful moment came with the four knocks..."
Russell also speaks of the Master:
"It's personal for the Doctor. The Master is his enemy, his opposite, and yet so tantalisingly close to being his soul mate. There's something epic about their sheer existence - the last two survivors of an ancient race. It's a clash of the titans. Both of them are heading for death, and yet both are determined to survive - at any cost!"
THANKS TO HEATHER FOR THE QUOTES