A lot of the new bonds will replace what's already been loaned to the government, so what will matter is the delta between the interest rates on the old bonds a

A lot of the new bonds will replace what's already been loaned to the government, so what will matter is the delta between the interest rates on the old bonds and new ones as well as whether the new bonds have different maturity times. So how much rolling the debt over will drive up interest rates is debatable though the issuance of new debt to finance the current deficit is more likely to do that. Of course, that assumes that there are buyers for the rolled over debt. The biggest source of financing over the past 20 years (China) isn't exactly happy with the US government right now. That could drive up interest rates on the bonds and cause problems.