First of all, we need a sense of proportion. Interest rates are low, they are very low. In fact, they are historically low. And the reason they are so low is because the FED is doing all the buying. Even not counting all the buying the FED is doing, the money they create is slushing around the system, a lot of it going back into government debt. Theoretically, the FED could cause the price of bonds to go to infinity and interest rates to plunge into negative territory if they purchased enough. Bonds are like any other instrument, their price is based on supply and demand and if the FED prints enough money and buys enough bonds, they can take their prices where ever they want. Of course what is holding them back is the price of the $$ (value of). That's the limiter on the FEDs actions. They could do whatever they want with the price of government debt, but they do not have the same control on the value of the $$.
So watching bonds is good, but the real tell is the value of the $$. Once that starts to fail, the FED will have to take action to stop the fall. The only action they can take is to decrease the supply of money by selling their bonds. At that point, interest rates will spike higher. But until then, the FED will have all interest rates extremely low.