''Sorry'' won't surpass Hello but her lead is getting smaller with each update so far. He just jumped 113 points from the last update. I guess we'll see how far he can go.
No other artist (besides that Country singer) has since come this close.
IMO Hello being #1 on iTunes Christmas Day seems highly unlikely. That would make 9 straight weeks at #1 digitally. She's selling so much right now it doesn't seem possible.
That said, I'm not convinced it would be Sorry at all. It could be a second Adele song or Katy's Christmas song?