Oh, I'm absolutely sure that Wilf would do that, throw the switch while telling the Doctor to go save Donna. Actually, when I first saw "The End of Time", I completely expected Wilf to throw the switch himself, just because RTD loves gut-punching Ten so much. I'm glad he didn't, because Ten's subsequent soul-searching rant and subsequent sacrifice is so beautiful and that's the thing that gets me bawling each time.