It's coming along nicely at the moment. The fed is being doveish but the bond yields are nearing 3% anyway.
and that's before they even start to taper QE. Not stop QE, taper it! When they taper and yields go to 3.5%+, then they will have to start up the printing presses again.
They can't afford to pay any real world valuation interest on their debt, so they need QE infinity. And more and more to keep rates low. Soon enough China will move away from USD (already happening), then boom, down goes the greenback!
Or Japan could explode first and everyone will see the similarity, then down goes the greenback!
Remember why interest rates are low. Its a market - governments sell bonds and the rate reflects the free market value of the debt. Right now, the US government pays a negative interest rate on 5 year bonds and just about breaks even on 10 year bonds. The reason its so cheap is that there is nowhere else to deposit a few trillion dollars risk free.
So the US, UK and Japanese governments will never have an issue with paying off debt at market rates as long as there is nowhere else to deposit large amounts of cash.