So many of the big villains lose a sense of menace because they never really seem to hurt the Doctor or the people close to him. If a character is going, its a great opportunity to kill them off. Moffat has already said that once the Ponds are gone there is no going back. They won't feature ever again.
Interestingly, this is one thing that has genuinely changed. Moffat doesn't kill people as much as RTD did, and the series has been significantly less blood soaked since he took over - not a complaint, just an observation. I don't think death is always the answer, as (more minor) people were often getting killed off in vast swathes in episodes then, and it happened too much and did start to lose its effect.
That said, talking to older Who fans, nobody seems to forget Adric, so perhaps it would indeed be massive.
One of the most enduring images of the entire series since its return for me is at the end of Series One, where Dalek fleets wiping out massive amounts of humanity was simply represented via some iconography on a screen with some dialogue. That was really awesome.
Torn on it. What I am keen for is that we don't end up with them showing up over and over again as RTD was obsessive with doing, so I'm glad Moffat has said they're gone for good. Could still find a way, as with Rose, but I hope he resists that temptation. Wouldn't mind one more visit to young Amelia in the same sort of way the Doctor visited pre-2005 Rose when his time comes, as a nod, but past that I really hope we have a clean break from them after this