Well, I think 2008's is still being tabulated and I think it's well beyond 455.
The debt is constantly being paid as treasuries are bought and sold continually. There was no hint at prescribed currency devaluation 2 years ago.
The debt to GDP ratio has been expected to decline as the dollar naturally weakened (you know, free marketstyle with no Chinese/ US govt manipulation) and US trade deficits declined. A 200 billion dollar debt increase in an 14 trillion dollar economy growing at 3% annually combined with a declining US dollar tends to support the expected debt ratio decline.
All bets are off for the time being on that now. Especially with a president making statements of trillion dollar debts into the forseeable future (someone told him that's not sustainable, on the job training is tough, and he's backed off that one).
We'll wait to see.